IN Engineering (vol. lxxxii., No. 2126) an abstract is given of a paper by Mr. A. R. Ledoux, presented to the American Institute of Mining Engineers, describing a new method of mining kaolin. Deposits in the Housatonic River district in Connecticut were being worked at a loss, owing to transport difficulties and to increase in expenses caused by the dip of the vein, which ran at an angle of about 50 degrees from the vertical, between gneiss and hornblende schist, and a footwall of rock. The material is therefore now mined by well, by which method the crude material is obtained with but little of the overburden, &c. The wells are from 50 feet to 198 feet deep, and contain a 4-inch, and, inside this, a 2-inch pipe. These go down gradually into the clay. Water at a pressure of about 40 lb. per square inch is forced through the smaller pipe, and on its passage upward carries with it about 5 per cent. of solid matter, of which 75 per cent. is pure kaolin.

MUCH valuable information regarding the mineral resources of Peru continues to be got together in the admirable series of monographs issued by the Government Corps of Mining Engineers. In Boletin No. 29 Mr. Federico G. Fuchs describes the copper-bearing region in the vicinity of Ica and Nazca. His detailed description, covering 100 pages, and his geological map show the importance of a mining centre that has long been neglected. In Boletin No. 35 Mr. Enrique I. Dueñas reviews the mineral resources of Jauja and Huancayo. At the present time no mines are being worked in these provinces, but the author shows that they are rich in coal, asphalt, copper, silver, gold, molybdenum, and iron. In Boletin No. 36 Mr. Luis Pflücker describes the iron-ore deposits of Aija and Calleycancha. The ore, which occurs in veins, is of great purity and richness, but the absence of fuel is, in the case of the Aija deposits, unfavourable to their development. The Calleycancha veins are more promising owing to their proximity to the Mancos coalfield.

THE address delivered by Mr. James Adamson, hon. secretary to the Institute of Marine Engineers, оп October 1, dealt in a scholarly manner with the advantages of a technical society. To the individual member, the advantages are in the direction of mental exercise, and consequent strengthening of the faculties of the mind; in the direction of finding out, in the course of discussions with fellow-craftsmen, how troubles in connection with details have been met and difficulties overcome; in the

direction of social intercourse, and in exchanging experiences for mutual benefit. The advantages to the community of which the members of the society are units are in tending to improve the conditions of life and work all round; in tending to bring to the front, for the benefit of all, the latest improvements and developments; in tending to educate the general public in respect to the various aspects of the world of science, and to give the people a better understanding of things within the domain of science. The advantages to the nation are in tending to improve the trade of the country by improving methods of manufacture; in tending to improve material and minimise risk of failure; in tending to lessen insurance premiums by lessening risk of breakages, stoppages, and disablements; in tending to the adoption of improved

methods, material and appliances, with better conditions of upkeep and improved views in respect to upkeep and expenditure, to get the best results in immediate running and prospective life average, thus minimising costs and economising capital outlay, with consequent advantages in competing for the traffic of the world; and in tending to re

duce the cost of material and running expenses and repairs, enabling employers to lessen the cost of output, and make improvements in their plant to enable them to keep up to date in their works and factories with all competitors.

DURING the past few years several theories have been advanced connecting the fluorescence of organic substances with their chemical constitution. A new hypothesis is now suggested by Profs. Luigi Francesconi and G. Bargellini, based on the examination of a very large number of substances by a very sensitive method which they have devised for detecting fluorescence (Atti dei Lincei, series 5. vol. xv., No. 3). When a beam of sunlight is concentrated by a lens on a solution of the substance contained in a test-tube in a darkened box, and the liquid is examined from above, the cone of light appears, in the case of fluorescent substances, of a different colour from that of the solution. The striking fact has been elicited that aliphatic substances do not show fluorescence, and the same holds true of alicyclic compounds in which fatty groups predominate. It is contended that all aromatic substances are potentially fluorescent, and that a greater or less degree of fluorescence is to be attributed to the presence of certain groups or radicals which enhance or diminish the effect, each group possessing a specific influence.

THE chemical and electrical effects induced by ultraviolet light in the case of certain elements have recently attracted attention, and explanations have been advanced based on the electronic theory of matter. In this connection an investigation of the photoelectric properties of anthracene, by A. Pochettino (Atti dei Lincei, series 5. vol. xv., ii., p. 171), has a special significance. It bas long been recognised that anthracene is highly fluorescent, and the author has recently proved that this fluorescence 18 accompanied by "ionisation" of the air in the neighbourhood of the anthracene. In the paper cited it is shown that the photoelectric effect of anthracene is very nearly the same as that of zinc, and that, as with zinc, the activity decays with time. This decay is, however, observed only when the layer of anthracene exceeds a certain thickness (0-02 mm.) and is attributed to the high dielectric properties of the material, which, by allowing the accumulation of a positive charge on the anthracene, arrests the ionisation effect. The original activity of anthracene which has completely lost its photoelectric properties can be restored, not only by leaving the material in darkness, but by exposing it during a few minutes to the radiation of radium, which serves to

neutralise the positive charge. The decay of the activity with time is capable of being expressed by an exponential curve. Similar results are noticed in the case of phenanthrene. The resemblance of the phenomena described to those characteristic of radio-activity again raises the question, suggested by Armstrong and Lowry in 1953. of the relationship of radio-activity and fluorescence. In the case of anthracene, atomic degradation is hardly probattributed to molecular transformation involving the change able; the fluorescence of anthracene is, indeed, generally of one structure into another under the influence of light Whether radio-activity is not also a molecular, as dis tinguished from an atomic, change, caused by an externa stimulus, similar to, if not identical with, light, is 4

question which naturally arises from the analogy presensi

by the two cases.

AN elaborate work on salt and salt mines is in course of publication by Mr. W. Engelmann, Leipzig, for the Vienna Academy of Sciences, under the title "Das Salz dessen Vorkommen und Verwertung in sämtlichen Staats

der Erde." The second volume, dealing with salt in Asia, Africa, America, and Oceania, appeared recently, and the first volume, which will be concerned with Europe, is in the press.

THE prominence now given to geometrical and machine drawing in the curricula of schools and colleges has led to an increased demand for trustworthy mathematical drawing instruments. The recent catalogue, with its numerous illustrations, published by Mr. W. H. Harling, of Finsbury Pavement, London, showing the instruments he is prepared to supply, may be commended to the atten

tion of teachers and students. In it they will find particulars concerning a great variety of instruments designed to meet every want.

JUPITER'S SEVENTH SATELLITE. From a telegram from Prof. Pickering to the Kiel Centralstelle, published in No. 4123 of the Astronomische Nachrichten, we learn that Jupiter's seventh satellite was re-observed by Prof. Perrine at the Lick Observatory on September 25. The positionangle and distance at 1906 September 25.9962 were 119°.1 and 2578" respectively.

OBSERVATIONS OF VARIABLE STARS.-Bulletin No. 8 of the Laws Observatory, University of Missouri, contains the results of some variable-star observations made at the

observatory during 1905-6. A grant of five hundred dollars from the Gould fund of the National Academy of Sciences has enabled the director, Prof. F. H. Seares, to engage an assistant observer, Mr. E. S. Haynes, for this work with gratifying results.

of

The star B.D. + 55°-2817 has been shown to be a variable of the continuous variation type, with a range of 0-4 magnitude and a period of 5:4 days. Observations V Lacertæ, V Vulpeculæ, and 108.1905 Capricorni are also recorded. In the case of the last-named, the rise to maximum is very rapid, an increase of 1.5 magnitudes taking place in 12 hours, and the observations show that this star is probably not of the Algol type.

SUN-SPOT SPECTRA OBSERVATIONS.-In No. 2, vol. xxiv., of the Astrophysical Journal, Mr. W. M. Mitchell, of Princeton Observatory, records the results of his sun-spot spectra observations made during the period October, 1005. to May, 1906. Mr. Mitchell found that during the more recent observations the number of "weakened lines in the spot spectra has increased considerably; many lines previously recorded as ** reversed " are now weakened," and new lines of the latter type are recorded. A sugges tion that this change may be a result of the passing of

66

the sun-spot maximum awaits the confirmation of further observations. Numerous cases of abnormal "reversals " are referred to in the paper. From the observations of reversed lines Mr. Mitchell deduces a temperature for the gases producing these lines of 4700°, and a further deduction gives 0.38 as the ratio of the sun-spot radiation to the radiation from the unaffected photosphere. The spectrum and construction of the chromosphere are also discussed at some length.

CONDENSATION NUCLEI.1

PROF. Barus has written more upon the subject of condensation nuclei than any other physicist. In the present memoir, as in those which have preceded it, he arrives at conclusions which are not in agreement with the work of others who have investigated the properties of ions and nuclei. If his investigations are to be trusted, the determinations which have hitherto been made of the

charge carried by the ions by means of the condensation method must be regarded as quite untrustworthy. The matter is of sufficient importance, therefore, to justify an examination of Prof. Barus's methods.

The first three chapters, and the greater part of the sixth and concluding chapter, are concerned with experiments upon the production of clouds by the sudden expansion of dust-free air initially saturated with water vapour, the air in most cases being exposed to the action of X-rays or radium. As described by Prof. Barus, the phenomena are exceedingly complicated and irregular. This is not surprising, however, being largely a result of complication in the experimental conditions.

The expansion was brought about by suddenly opening communication between the " fog chamber" and another much larger, partially exhausted vessel, a measured fall of pressure being thus produced. By means of the coronas formed, an estimate was obtained of the size, and hence indirectly of the number of the drops; filtered air was then re-admitted to bring the pressure back to that of the atmosphere. This method of effecting the expansion is not a suitable one for investigations of the kind attempted. For the rate of fall of pressure must diminish as the expansion approaches completion; it is probable that with a suitable width of connecting tube no great error will be introduced into the measurement of the least expansion required to produce a cloud (i.e. that the expansion may be made practically adiabatic), but it is unlikely that the maximum degree of supersaturation resulting from expansions greater than this approaches at all closely to that calculated from the pressure fall. For the condensation on the nuclei which first come into action will, by reducing the amount of vapour remaining uncondensed and by the heat set free, prevent the full supersaturation corresponding to the pressure fa!! from being attained. The larger the number of easily caught nuclei, the more will the maximum supersaturation attained fall short of the theoretical. The method is thus not a suitable one for obtaining information about the number of nuclei corresponding to various degrees of efficiency.

re

If we produce a cloud in dust-free air upon nuclei which require a high degree of supersaturation to make water condense upon them, the drops which are formed, if caused to evaporate by compression of the air, appear to leave behind nuclei requiring only a slight supersaturation to make water condense upon them. Unless these are moved before expansions large enough to catch the original nuclei are again attempted confusion is sure to follow. The result of neglecting this precaution is not merely that these residual nuclei give rise to drops as well as those under investigation, but unless the apparatus is such as gives exceedingly efficient expansion the supersaturation necessary for the capture of the nuclei under investigation may not be attained, the number of drops produced being thus too small in contrast to what might at first sight be expected. The experiments of Prof. Barus's investigation were performed under conditions which made this effect 1 "The Nucleation of the Uncontaminated Atmosphere." By Prof. Carl Barus. Pp. 152. (Published by the Carnegie Institution of Washington January, 1906.)

conspicuous, the result in many cases being a remarkable alternation of larger and smaller coronas, corresponding to variations in the number of the drops, for successive expansions of equal amount. It is easily seen how, under

the appropriate conditions, such an alternation may arise, for the second expansion may remove the greater number of the residual nuclei due to the first, so that the third takes place under conditions similar to those of the first expansion. A large amount of space is given to the study of these alternations, and they are finally traced to their true source after many hypotheses have been suggested for their explanation, "the solutional enlargement" of the nucleus, as the author calls it, being then apparently regarded as a new discovery. Besides incidental references to these residual nuclei in earlier papers, he would have found them described in Thomson's "Conduction of Electricity through Gases, p. 139, or in a review of the subject of condensation nuclei presented to the International Electrical Congress of St. Louis in 1904, and a great deal of labour might have been saved. That small drops of pure water might be expected to cease to evaporate, even in an unsaturated atmosphere, beyond a certain minimum size (related to the thickness of minimum surface tension of thin films) is pointed out by Thomson in the same chapter, p. 153; and a theory (having a similar basis), which explains the permanence of certain slow-moving ions requiring a negligible degree of supersaturation to make water condense upon them, has been given by Langevin and Bloch.

By exposing to intense X-rays the moist air in a "rectangular condensation chamber of wood impregnated with resinous cement,' "the front and rear faces being of plate glass, persistent nuclei requiring only a very slight expansion to cause water to condense upon them were obtained. The only nuclei hitherto observed in dust-free air exposed to X-rays require large expansions to capture them. That such nuclei should, under the appropriate conditions (the occurrence of chemical action giving rise to soluble products), grow into larger bodies is what might be expected; such a growth has, for example, been observed in the case of the ions arising from a point discharge. It is quite likely that sufficiently intense X-rays or radium rays might bring about in moist air the chemical action necessary for such a growth of the nuclei, as intense ultraviolet light certainly does; but results, obtained with a chamber of wood impregnated with resinous cement and not rigorously shielded from all possible direct electrical effects from an X-ray bulb placed a few cm. from it, are not free from ambiguity.

Apart from this effect of very intense radiation, the conclusions arrived at by the study of the effect of X-rays and radium rays appear to differ from those of other observers. Prof. Barus holds original views, not only upon the relation of "nucleation" to ionisation, but as to the nature of the radiation from an X-ray tube. These are best given in his own words :

Chapter vi., p. 133: "Let the X-radiation to which the dust-free air is exposed be relatively weak, so that the density of ionisation may remain below a certain critical value. The nuclei observed on condensation are then very small, and they require a high order of exhaustion, approaching but always below the fog limit of nonenergised air. They are usually instantaneously generated (within a second) by the radiation, so that their number is definite independent of the time of exposure. They decay in a few seconds after the radiation ceases, i.e., roughly, to one-half their number in 2 seconds to one-fifth in 20 seconds, in the usual way. I fancy that these nuclei are what most physicists would call ions; but nevertheless the particles are not of a size, the dimensions depending on the intensity of the penetrating radiation to which they are usually due, and they pass continuously into the persistent nuclei, as shown in the next paragraph, where decay of ionisation and of nucleation are very different things. They are abundantly produced by the y rays. which though weak ionisers, become from this point of view strong nucleators."

Chapter vi., p. 142: While the phosphorescent, photographic, and electric effects of X-radiation decrease rapidly with the distance, D, from the tube, the nucleating effect (N, nuclei generated per cubic centimetre, instantly) is

The law of inverse squares would predicate a reductuum of 10,000 to 1 between these limits; and in fact, at 6 m the phosphorescent screen is intensely luminous, at 200 cm very dim, at 600 cm. quite dark as in the case of any ordinary illumination. The leaves of an electroscop within a glass bell jar collapse in a time which is directly as the square of the distance from the energised X-ray bulb. The result obtained with nuclei is astonishing - the nuclei-producing radiation would, at first sight, seem to be of an extremely penetrating kind, akin to the gamma rays of radium, and distinct from the ordinary phosphorescent producing X-rays."

Chapter vi., p. 144: "To the eye of the fog chamber therefore the walls of the room are aglow with radiation, and no matter in what position the bulb may be placed (observationally from 6 cm. to 6 m. between bulb and chamber) the X-illumination as derived from primary and secondary sources is constant everywhere. It is to he understood that the X-illumination here referred to may be corpuscular. In fact, so far as I see, the primary and secondary radiation here in question may be identical; for the corpuscles may come from the circumambient molecules shattered by the shock of gamma rays."

Chapter vi., p. 145: "It has been shown that for very short exposures (sections 101 and 102) the nucleation ithe same, whether the bulb is placed at 6 cm. or 6 m. from the fog chamber. But only in the former cast (D=6 cm.) is the effect cumulative; only for very short distances will persistent or very large nuclei appear if the exposure is prolonged several minutes. I have therefor suspected that the radiation from the X-ray bulb is twofch in character; that the instantaneous effect (fleeting nuclei is due to a gamma-like ray, quick moving enough to pene trate several millimetres of iron plate appreciably even for D=6 metres; furthermore that the cumulative effect (persistent nuclei) is due to X light, properly so called. which produces the usual effects subject to the laws ol inverse squares; but it is noteworthy that while the penetration of X-rays is relatively small, and the distance effect negligible (section 101), they are both large for the radiation from radium (section 104)."

not

The conclusion that the nucleus-producing radiation frem an X-ray bulb is constant over distances varying from 6 em. to 6 m. (or as elsewhere expressed that "the whole medium within the room is almost equally energised throughout ") is somewhat startling. One would expect the number of nuclei present at a given moment in any case to fall off inversely as the square of the distance the number of ions might under suitable conditions he expected to vary inversely as the distance; but the fact that there is no falling off at once suggests that there is something wrong with the experiments or the interpretation put upon them. Possibly the observed constanct partly due to the failure of the method to deal with men than a limited number of nuclei. Some of the results however, suggest that it may have been partly due to the failure to shield off the rapidly changing electric field pro duced by the working of the coil.

There is more danger of the statements of the firs paragraph quoted above leading to confusion. The ex pression "fog-limit" apparently indicates the smalles pressure fall which produces a sufficiently large number of drops to admit of a corona being observed. Previes expansion experiments, in which a sudden definite volumes change was produced, have shown three critical or limiting values of the expansion (measured by the ratio of th final to the initial volume). These are 138, bevond which dense fogs begin to be produced in dust-free air under normal conditions; 1-25, the least expansion required ter the capture of negative ions; and an intermediate one the neighbourhood of 1-31, the least expansion require! for the capture of positive ions. Certain apparently charged nuclei require an expansion of about the sare amount as do the positive ions. Ions of both kinds always present in small numbers in the air of a came

essel unless an electric field is present to remove them as they are set free; an expansion exceeding 1-25 gives, in the absence of such a field, fog or rain, according as the air is exposed to external ionising agents or not. The above three limits would correspond to adiabatic pressure talls of 27-7, 20-5, and 24-1 cm. of mercury respectively, if the initial pressure was 76 cm., and would vary with the initial pressure. The fog limit obtained by Prof. Barus for air exposed to X-rays or radium rays, except under conditions such that persistent nuclei resulted, generally lay between 19 and 21 cm., except when the radiation was exceedingly weak, when the limit approached that which he obtained for non-energised" air, about 24 cm., which may be compared with the intermediate critical expansion mentioned above. The results of Prof. Barus are accounted for if we suppose that his method failed to detect the comparatively small number of drops formed on the spontaneously produced negative ions; such variation of the limit as was observed in air exposed to external radiation, as the intensity was varied within moderate limits, being what might be expected with a method in which the " fog limit" is only reached when a certain minimum number of drops is exceeded. It is true that the ions are not at any one moment all in an equally favourable condition for helping condensation, a certain range of expansions (not very wide, however) being required, for example, to catch all the negative ions; but there is no evidence that the efficiency of the ions as nuclei increases with the intensity of the ionising rays, if we leave out of consideration the possible effect of exceedingly intense rays; for the weakest radiation (that responsible for the " spontaneous ionisation), as well as for radiation of very considerable intensity, the efficiency of the most favourably situated ions remains the same. Prof. Barus has apparently failed to notice that the limits found by him are, if properly interpreted, in fairly good agreement with those of previous observers quite as good agreement as could be expected from the comparative roughness of his methods. Possibly some explanation of this omission is afforded by a passage on p. 50, where the volume change corresponding to a given pressure fall has been wrongly calculated, as if the expansion were isothermal instead of being nearly adiabatic.

It is a matter of some difficulty to know what views Prof. Barus really holds upon the relation of the ionisation ક determined by electrometer measurements and the

fleeting nuclei which "most physicists would call ions." That he does not regard such nuclei as identical with the ions is plain from the statement that the gamma rays, though weak ionisers, are strong nucleators, as well as from the suggestion that the fleeting nuclei produced by an X-ray bulb may be due to a gamma-like ray," and only the persistent nuclei to the " X-light properly so called, which produces the well-known effects subject to the law of inverse squares (the ionisation as determined by electrometer measurements being one of these, as another of the passages quoted seems to indicate). Prof. Barus seems to have entirely failed to realise how complete is the evidence of the identity of the nuclei produced, in the investigations of previous observers, by X-rays or any of the various types of Becquerel rays with the ions the existence of which has to be postulated to explain the phenomena of the conduction of electricity through the air exposed to such rays. Not only has it been shown by direct experiments that the nuclei are positively and negatively charged bodies having properties such as have to be assigned to the ions to explain the phenomena of conduction through gases, but a still more direct proof of the identity is furnished by the agreement of the two methods by which the charge on the ions was determined, that of J. J. Thomson and that of H. A. Wilson. For the former gives the ratio of the ionisation (the product of the number of the ions per c.c. and the charge carried by each), as determined by electrical methods, to the number of the nuclei, while the latter gives directly the actual charge of a single nucleus. Thus the number of nuclei, multiplied by the charge on each nucleus, is equal to the product of ionic charge and number of ions deduced from electrical measurements. The ionisation accounted for by the nuclei in question is thus equal to the ionisation determined by the electrical method.

Chapters iv. and v. contain an account of observations made at Providence and in the comparatively uncontaminated atmosphere of Block Island upon the variations in the number of nuclei in unfiltered atmospheric air. The nuclei are here such as may be caught with smaller expansions than are required by the ions; they are Aitken's "dust" particles. Their number was estimated, not by Aitken's method, but by observing the coronas seen through the fogs produced on expansion of the air in an apparatus of the same type as that used in the investigations already discussed. In the present case, where only easily caught nuclei are involved, the objections brought above against the method do not apply, and there can be no doubt about the importance of such investigations. C. T. R. WILSON.

BOTANICAL CONGRESS AT HAMBURG. THE Society of Applied Botanists held its annual conference at Hamburg in September, and the Society of Systematic Botanists held its meeting there at the same time. Some 150 botanists in all, mostly interested in applied botany, attended. The choice of place of meeting was a happy one, as in Hamburg, the chief Continental port, the closest connection can be seen between commercial and scientific activities.

All the botanical institutions are under the direction of Prof. Zacharias, and while the educational requirements are well cared for, everything that the botanical scientific staff can do to foster the trade of the city is done. The seed-testing station is under the direct charge of Prof. Voigt, who, with six assistants, tests some 1500 samples of seed, oil-cake, &c., each year. An important export seed trade with the Argentine Republic is carried on, the certificates required by the Republic being supplied from the station. Another important institution is the Station for Plant Protection, founded some seven years ago as a means of protection for the vineyards and orchards of Germany against the San José scale insect and other pests liable to be imported into Germany on American apples, fruit-trees, &c. This station is in charge of Dr. Brick, who, armed with the necessary staff, library, and apparatus, must report on every barrel of apples coming into port. The rejected apples, dangerous to Germany, find a ready market in England and elsewhere.

In the Botanical Museum the collections are arranged in two sections. One part follows the usual lines-the specimens are arranged in systematic order, according to their natural affinities, and serve more especially for educational purposes. The other part of the collection appeals

to commercial interests. The fibres of commerce, the chief rubbers, gums, resins, cereals, &c., are in each class grouped together, regardless of natural affinities, and solely for trade purposes. A new and more commodious museum

in the Botanic Gardens is just reaching completion. The museum is regularly visited by schools and their teachers, and a large piece of ground is set apart in the suburbs to supply the specimens required in the schools for teaching purposes.

Everything that could be was done by the local botanical staff and others to make the meetings of the societies a success. The Hamburg Government granted a sum of 4000 marks toward expenses, and in other different ways showed a practical interest in the proceedings. One important feature was the first International Conference on Seed Testing. Most of the seed stations in the world were represented, and attempts to establish a uniform system of testing, applicable in different countries, were discussed. It was generally felt that it would be premature to seek to go further at present than simple discussion. Many valuable papers were contributed. Dr. Stebler gave the results of twenty years' investigation in the station at Zürich as to the country of origin of the seeds of commerce, judged sometimes from the particles of soil found in the impurities (!), but more usually from the weed-seeds present. This paper was fully illustrated by dried plants and seeds. Dr. von Weinzierl, of Vienna, dealt with sugar-beet and mangel seeds; Dr. Degen, of Budapest, with dodder in clover; Prof. Rodewald, of Kiel, with the sources of error in seed-testing; while Prof. Voigt, of Hamburg had pre

pared a comparative report embodying the rules governing seed-testing in Germany, Russia, Scandinavia, and the United States of America. Surprise was expressed that there was only one Government seed station in the United Kingdom-that in the present writer's charge in Dublin, where during the past year 1476 samples were examined.

A paper which aroused considerable interest was that by Prof. Warburg urging the claims of tropical agriculture on behalf of the German colonies, and the conference adopted resolutions urging the necessity of :-(1) The erection of a central imperial institute in connection with the Biological Institute at Dahlem, for the study of tropical agriculture and forestry. (2) Conversion of the botanical garden in Victoria, in the Cameroons, into an agricultural institute of the first order. (3) Foundation of similar institutes in Togo and the South Sea Islands. Prof. Warburg thought that a banana trade in German West Africa could be developed, that rubber could be made available in increasing quantities by cultivation of rubber trees, and that mistakes had been made by attempts to apply to tropical countries the crops and methods of cultivation found to succeed in Germany.

Many important papers on other subjects by Profs. Drude, Zacharias, Aderhold, Appel, Vañha, &c., were read, but limitations of space prevent further mention here. A detailed official report is in course of preparation. The systematists, with Dr. Engler as president, devoted one day to the Heide near Wintermoor, where, under Dr. Graebner's guidance, fine specimens of native Juniperus, and many other features, wild and cultivated, of the moor, which is of enormous extent, were seen. While attempts are being made to restore to profitable cultivation land which is now in possession of heather, and was formerly covered with oak and beech, one portion, some fifty acres in extent, near Totengrund, has been bought by Prof. Thomsen, of Münster, and presented by him to the nation as a permanent nature memorial.'

T. J.

METEOROLOGICAL OBSERVATIONS.

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TERRESTRIAL Physics in Messina.-The Annuario of the Messina Observatory for the year 1905 shows that Prof. G. B. Rizzo has made a good beginning in the important task recently imposed upon him by the faculty of the university. The climate of Sicily is fairly well known so far as the principal towns concerned, thanks to the efforts of the directors of the large observatories of Palermo and Catania and others, but, as Prof. Rizzo points out, little or nothing is known about the conditions of the other parts of the island. To remedy this want a number of rainfall and temperature stations have been established during the last year in the province of Messina, and have recorded observations from the beginning of 1906. On the initiative of the International Meteorological Committee, the Solar Committee of which Sir Norman Lockyer is president is carrying out an important study of the connection of solar and terrestrial phenomena; for Italy, Prof. Riccò at Catania and Prof. Rizzo at Messina are actively engaged in the investigation on the general plan laid down by the committee. For the study of earthquake phenomena one of Vicentini's microseismographs has been erected; in connection with this subject Prof. Rizzo is investigating the facts relating to the terrible Italian earthquake of September, 1905, with the cooperation of more than eighty observatories in various parts of the world. The seismograms show that the disturbance was felt from Norway to the Cape of Good Hope, and from California to New Zealand. The complete results will shortly be published.

Meteorology in the United States.-The report of the U.S. Weather Bureau for the fiscal year 1904-5 (pp. xxiv+ 384) gives a brief survey of the development of the weather service during ten years' administration of the present chief (Prof. W. L. Moore). The magnitude of the work now performed by it is almost astounding; indeed, Prof. Moore claims that in the results accomplished for the benefit of the farmer, the sailor, the seeker after health or pleasure, and others, there is no weather service in the world comparable with it. The estimated amount of the

expenditure for the year exceeded 278,000l., and the appropriation for the following year, including the support of Mount Weather Observatory (Virginia), an institution devoted purely to meteorological research, exceeded 290,000l. The supervising director of that observatory is Dr. W. J. Humphreys, late professor of physics in the University of Virginia, and Prof. Moore states that Mount Weather may be expected to do as much for the science of meteorology as the service has already done for the material interests of the United States. It is stated that the daily distribution of weather forecasts and charts has increased to nearly 623,000, of which 158,000 represent printed reports. Weather maps are printed at nearly 100 local stations, and daily telegraphic reports are received from the Azores and west coasts of Europe, and the Bureau has developed one of the best wireless systems now in use. The Navy Department has instructed its wireless stations to receive and promptly transmit to the ocean or other places where the information can be made useful the storm warnings of the Weather Bureau, and has requested vessels having the use of its wireless stations to take observations and to transmit them to the Bureau, without charge against the Department of Agriculture. With a further extension of wireless telegraphy, it is thought that the reports will render possible a storm-warning service for the western coasts of Europe and for vessels in midocean. Arrangements have been made for aerial research by liberating unmanned balloons from many stations, in cooperation with those at Mount Weather.

The last semi-annual Bulletin of the Colorado College Observatory contains the annual meteorological summary for 1905. The present observatory, erected in 1894, is about 6040 feet above sea-level, and was the gift of Mr H. R. Wolcott, of Denver; the director is Dr. F. H. Loud. It is well equipped with astronomical and self-recording meteorological instruments; the college became a voluntary station of the U.S. Signal Service in 1878. The mean temperature of the year 1905 was 46°-1, mean maximum 58.8, minimum 33.5, absolute maximum 91°, in June and August, minimum -22°, in February. The yearly rainfall was 15.9 inches, number of rain-days 70. The Bulletin also contains monthly summaries of weather records at Colorado Springs between 1872 and 1903, which have been collected from various sources with considerable labour by Mr. C. M. Angeli, and prepared for press by Mr. C. D Child; their present publication is merely preliminary in view of numerous demands for historical information, and is subject to later revision.

Observations in Mauritius.-The annual report of the director of the Royal Alfred Observatory, Mauritius for 1905, shows that the rainfall there was much above the average of the last thirty years, viz. 6700 inches as compared with 48-27 inches; in January the fall was 21.16 inches, or 12.77 inches above the normal, and is the greatest on record. The maximum shade temperature was 890, in November, and the minimum 52.3, in August; the highest temperature in the sun's rays was 1564, in January, the highest on record being 1653 in February, 1898. From observations obtained from ships' logs, the tracks of seven cyclones in the Indian Ocean were laid down; 474 photographs of the sun were sent during the year to the Solar Physics Committee. Fifty-three earthquakes were recorded. The registered velocity of the wind was below the average in every month except April Mr. Claxton remarks that a comparison of the records of the Robinson and Dines anemometers in use at the obserT – atory in the years 1904-5 indicates that one or both are untrustworthy as standard instruments.

Rainfall in German South-West Africa in 1904-5.-Nowithstanding the considerable damage and loss of recrras due to the rebellion of several tribes, complete results from twenty-eight stations are published in Wissenschaftl Beihefte zum deutschen Kolonialblatte, Band xix., 2 Heti. The total number of stations which have suffered during the last two years amounts to forty, but steps are being taken to replace the instruments as soon as practicable The rainfall of the year in question was, on the average only about three-fourths of that in the previous year the central and southern parts only about one-half The principal rains fall between January and March; the greate