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Birds" in volumes of simultaneous issue with his volumes of birds. This egg-book of Mr. Hume's is one of the best oological works ever published, and has long been out of print. A good deal of the additional matter which Mr. Hume had accumulated for a second edition, was stolen by a dishonest servant, and sold for waste paper in the Simla Bazaar, but enough has remained to enable Mr. Oates to put before us a very interesting record of the breeding habits of Indian birds; and if any tribute be wanted to Mr. Hume's energy and ability, the reader has but to refer to the present work, to study the oological records of the best circle of field-ornithologists which ever rallied round the central figure of any zoologist. The portraits of naturalists who have contributed to the development of our knowledge of Indian birds lend an additional interest to Mr. Oates's volume on the "Nests and Eggs of Indian Birds."

R. BOWDLER SHARPE.

EPHEDRA.

Die Arten der Gattung Ephedra. Von Dr. Otto Stapf. Pp. 112, 1 Map and 5 Plates. (Vienna R. Tempsky, 1889.)

:

It is extracted from the second part of the sixteent volume of the Denkschriften der Mathematisch-Naturwissenschaftlichen class of the Kaiserlichen Akademie der Wissenschaften in Vienna. Dr. Stapf is one of the officials of the Botanic Garden of the University Vienna, and has had the advantage of full command of material, both in the way of specimens and books. Im of the plates and a large proportion of the letterpress are devoted to the anatomy and morphology of the vegetative and reproductive organs of Ephedra. In the structure of the woody bundles Gnetaceæ establish some links of transition between Conifera and the typica Dicotyledons. Ephedra approximates in some points towards Casuarina. In the veining of its well-developed leaves Gnetum recedes from the ordinary Gymnospermous type. In Ephedra there is an unmistakable perianth to the male flower, but the homology of the outer wrapper of the seed is not so clear. Then follows the systemat.c portion of the monograph. Dr. Stapf admits twentyeight certain and three imperfectly-known species, and for each of these he gives a diagnosis, a figure showing its essential characters, an extended description, and i full account of its synonymy and geographical distribution. He makes three sections, Alatæ, Asarea, and

EPHEDRA is one of the three genera of the small Pseudo-baccata, dependent mainly upon whether the seed

Gymnospermous order Gnetaceæ, the two others being Gnetum and Welwitschia, that most curious of all gymnospermous plants. Ephedra is a type of remarkable habit, specially modified, though in a different way from Welwitschia, to inhabit the dry and sandy regions of the world. It has shrubby stems, with copious slender, whip-like, straight or turning branches, foliar organs and flower-wrapper reduced to a minimum, unisexual mostly dioicous flowers in small catkins with dry imbricated scales, the female catkins containing one or two flowers

only, and the males several, with from two to eight stamens with the filaments usually joined in a column. The species are numerous and difficult of determination, partly because the leaves are nearly suppressed, partly because the stems of all the species are very similar, and that it is needful to have both staminate and pistillate flowers to study before any given plant can be determined confidently.

The map shows clearly at a glance the geographical range of the genus. It surrounds the basin of the Mediterranean, climbs the lower levels of the Central European Alps, attains its highest development in Central Asia, reaching southward to the north of India and all through Arabia, northward to Lake Baikal and the Ural Mountains, and eastward to the western provinces of China; and reappears in the New World—in North America in California and Mexico, and in South America in the Andes and over a wide area south of the tropic from Chili across to Buenos Ayres. Though spread so widely over extra-tropical South America, it does not reach either the Cape or Australia, where the climate and soil seem so suitable for it. None of the single species have a very wide range, but it is one of the instances where a well-marked, sharply isolated generic type is represented in many different geographical areas by distinct specific types.

The present monograph is one of the best and most complete works of the kind that have lately appeared.

is fleshy in a mature state, or dry and furnished with a wing. Then follows a list of local names, and a very ful. list of the books in which the genus is noticed, extending from Gerarde and Ray down to the present time. The monograph is one that deserves to be studied carefully, both by structural and systematic botanists.

OUR BOOK SHELF.

J. G. B

Geological Mechanism; or, An Epitome of the Histor
of the Earth. By J. Spottiswoode Wilson, CE
(London and Manchester: John Heywood, 1300)
THE nature of this little work of 135 pages will be bes
indicated by a brief statement of its contents.
The book
is divided into three portions of not very unequal length
The first of these is "autobiographical," and relates.
with much circumstance, the author's adventures at the
Geological Society and Club, where, on the invitation of
the late Sir Roderick Murchison, he read a paper in the
year 1854. This is followed by an account (his own of
the causes which led to a disagreement between himself
and the leaders of an exploring expedition of which he
had been appointed a member. This part of the book is
relieved from the charge of being prosaic, however, by
the introduction of some very remarkable, and undoub
edly original verses.

Having devoted more than forty pages to himself, the author has left for the earth little more than fifty page more; and in this space he contrives to dispose of a great number of highly important problems, beginnin with "intelligence supreme; the nebular theory of La place; hypothesis of incandescence; theory of the c talline rocks; hypothesis of metamorphism," &c.; and finishing up with "the lunar, magnetic, and solar tides. the progressive desiccation of the atmosphere and earth the change of time; and the theory of creation."

Comprehensive as is this portion of the book, however. the author still finds much to put into his third part, or appendix-such as, "tails or atmospheres of planets and comets; the magnetic pole and change of climate. the magnetic tide of the atmosphere, &c." As in the first part he rose into poetry, here, in the appendix. he

soars into the realms of prophecy, and tells us about the climate which may be expected in these islands in the years 1970, 2020, and 2130!

The author assures us that he writes especially for civil engineers, and is not careful to conceal his contempt for "prominent men in other branches of science" and their opinions. But as there are some works "profitable for instruction," so there are others calculated to afford amusement; and it is very hard indeed that civil engineers should have a monopoly of all the fun that is to be got out of this one.

The Scenery of the Heavens. By J. E. Gore, F.R.A.S. (London: Roper and Drowley, 1890.)

THE title of this work is so suggestive of pictures that one cannot help feeling disappointed with the limited number of illustrations, especially as the book is designed for general readers. We look in vain, for example, for representations of Saturn and Mars, solar prominences, and many other celestial objects, of which no descriptions can convey so much to the mind as good illustrations. Some of the illustrations are reproduced more or less faithfully from photographs by Mr. Roberts and the Brothers Henry, but we regret to note that the wonderful photograph by Mr. Roberts of the Great Nebula in Orion is not amongst these. We may suggest also that in future editions some account be given of the instrument which reveals to us the greater part of the scenery of the heavens."

On the whole, the text is excellent, and will no doubt greatly interest the general reader. There is, however, a very loose statement on p. 24-namely, "if we assume that the attraction of gravitation at the earth's equator is 322 feet, we have the accelerating force of gravity on the sun equal to 895 feet per second." One of the most notable features of the book is the large number of poetical selections having reference to astronomical phenomena. The book contains a good deal of information, in some cases perhaps too much to serve the avowed purpose of the author, unless his readers intend to become amateur observers. The long lists of red stars, doubles, variables, and star clusters, for example, are much too detailed for general readers, although not sufficiently so for regular observers. The chapter on variable stars, as might be expected from Mr. Gore, is especially good. There is also an excellent chapter on shooting-stars, by Mr. Denning, who is eminently fitted for such a task.

We may remind Mr. Gore that probably no one now supposes that the so-called "gaseous" nebulæ consist of nitrogen (pp. 197, 206), and that the structure of the Great Nebula in Andromeda as revealed in Mr. Roberts's photograph indicates that the nebula is probably not "a vast cluster of very small stars placed at an immense distance from the earth" (p. 204).

No attempt is made to touch upon any theoretical astronomy, and the scope of the book is therefore correctly described by the title.

A Trip through the Eastern Caucasus. By the Hon. John Abercromby. (London: Edward Stanford, 1889.) Is it worth while for a traveller to make a six weeks' tour the subject of a book? Probably most people would answer promptly and emphatically, No; but any one who reads Mr. Abercromby's work will see that the reply may be wrong, and that everything depends on the nature of the scenes visited, and on the traveller's ability to give an account of his impressions. In the course of sx weeks Mr. Abercromby twice crossed the main chain of the Caucasus by passes which are little used except by natives. He was fortunate enough to secure, through the instrumentality of Prince Dondukoff Korsakoff, the Governor-General of the Caucasus, a circular letter in Russian and Arabic to all in authority wherever he might

wish to go. This, he says, acted like a charm, securing for him at every place the utmost hospitality. He had, therefore, the best possible opportunities of seeing what he desired to see, and of forming just opinions as to the characteristics of the people whom he visited.

Particularly good is his description of the strange village called Kubachi, in which there was at one time a flourishing school of the higher kinds of artistic craftsmanship. The village is "a long, narrow, extremely compact agglomeration of houses, built on the southern face of a very steep slope with a shallow ravine on both sides." A high round tower, commanding a wide view, stands at the top. All the roofs are flat, and, seen against the sky, the profile of the village is not unlike "a gigantic staircase." Before reaching Kubachi, Mr. Abercromby heard all sorts of wonderful stories about the inhabitants, and was assured that they were of Frankish origin. He found that there was nothing specially European-looking in the type of face either of the men or women. They appeared to him "quite like the Lesgians, though milder in their manners, and less wild-looking." Their speech has no sort of relation to the Indo-European languages, but belongs to the Lesgian family. There are in the village many sculptured stones and other relics of a period when the workers of Kubächi had a genuinely artistic impulse; and of these remains Mr. Abercromby gives a remarkably clear and attractive account. Not less interesting in its way is his description of the extraordinary wall of Derbend, which, according to the current native belief, is 3000 years old. For this idea there is of course no real foundation. Mr. Abercromby, with the enthusiasm of a thorough antiquary, investigated this structure with the greatest care, and even readers who are not generally attracted by archæological research will find much to please them in his narrative. Altogether, the work is fresh and bright, and we recommend it to the attention of those who find in good works of travel intellectual refreshment and stimulus.

LETTERS TO THE EDITOR.

[The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of NATURE, No notice is taken of anonymous communications.] The Royal Society's Catalogue of Scientific Papers: a Suggested Subject-Index.

THE method advocated by Mr. J. C. McConnel (NATURE, February 13, p. 342) would undeniably be feasible. But I should pity the fellow-craftsman who should have to carry it out. The idea of numerical subdivision has been worked out by Prof. Dewey with great ingenuity and industry in his "Decimal Classification and Relative Index," 1885. We find, on referring to p. 31, that o16.9289551 will indicate the "Bibliography of Persian poets." Natural science occupies a place from 500-600, and does not seem to have been as yet reduced to an equal degree of elegant simplicity, for the subject of "observing chairs, &c.," is merely denoted by 522.28.

After this it does not seem over bold to pronounce the result one of the most amusing things in cataloguing literature. It is, however, surpassed by Mr. J. Schwartz's " King Aquila's Library," in which the system is fairly demolished. But the London inquirer into the actual working of such a cumbrous device may gain a useful hint by noting that at the Guildhall Library there is an alphabetical index to these totally unnecessary would, of course, be an absolute necessity in the proposed case. numbers. Indeed, one is found in Prof. Dewey's own book, and

No, a good subject-index can be constructed on much simpler lines. See, for example, Poole's "Index to Periodical Literature," which includes in its first supplement (1882-87) some 1090 volumes (indexed in 483 pages). Another example may be found in the subject-index at the end of the "List of Books of Reference in the British Museum Reading Room," 1889. In this some twenty thousand volumes are included, which would

lead one to suppose that the size Mr. McConnell suggests is ample, not to say generous. I had hitherto supposed that a scientific writer does not necessarily treat of a fresh subject each time he writes.

Might I add that an index is not a pedigree or diagram, any more than a gazetteer is the same thing as a map? I fear that to mix up such distinct things would merely introduce an altogether needless difficulty. A CATALOGUER.

The Period of the Long Sea-Waves of Krakatao. IN connection with the great explosion at Krakatão at 10 a. m. on August 27, 1883, a great wave was generated, which at Batavia, 100 miles distant, reached a height of 73 feet above the ordinary sea-level. It was followed by a fairly regular series of fourteen waves, at intervals of about two hours, gradually diminishing in height. Captain Wharton, who writes this part of the Royal Society Report, is much puzzled by the long period. He says:" If the wave was caused by any sudden displacement of the water, as by the falling of large masses of ejected matter and huge fragments of the missing portion of Krakatão, or by the violent rush of steam from a submarine vent through the water, it is hardly to be conceived that two hours would elapse before the following wave, the second of the series, started after it. . . . If, however, upheaval of the bottom of the sea, more or less gradual, and lasting for about an hour, took place, we should have a steady long wave flowing away from the upheaved area, which as it approached the shore would be piled up considerably above its normal height. Thus these waves of long period would be set up. The water would flow back on the motion cea-ing.' I do not understand how the series of waves would be produced by the sea-bottom being upheaved in the manner described. When the upheaval ceased, the water would probably flow back, and, after the centre of disturbance was reached, a second wave would be generated. But there would be no reason for the water flowing back a second time, and no more waves would be generated. Further, in another part of the Report, we find Prof. Judd expressing the opinion that no upheaval has taken place (p. 25).

...

Another explanation has occurred to me, which seems satisfactory. Let us assume, with Prof. Judd, that the first wave was due to a great quantity of fragments falling into the sea. This wave would be reflected by the shores of the Straits several times backwards and forwards, each time giving rise to a fresh disturbance, travelling out towards Batavia through the narrow opening to the east. Opposite Krakatão both on the northern and on the southern shore of the Straits is a great bay. time a wave would take to travel from Krakatão to the head of the bay on the north is given by Captain Wharton at sixty-one minutes, and the distance to the head of the other bay is much the same. This agrees very well with the two-hour period. Moreover the first disturbance at Batavia would be a rise of the water, which was the case.

The

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The Distances of the Stars. YOUR note of Prof. Eastman's address to the Philosophical Society of Washington in your columns of February 13 (p. 351) raises some questions of interest on which I think the Professor is mistaken.

As regards the nearness of particular stars, there are several indications which astronomers have sought to verify by observation and computation. One of these is brightness; a second is large proper motion, and a third is a binary system easily separated by the telescope (especially if the period is comparatively short). Some persons have also supposed that red stars, variable stars, &c., are nearer than most of their neighbours. Stars possessing one or more of these characteristics have been selected for parallax measurements.

One of these characteristics being brightness, almost every bright star in the northern hemisphere and a good many of those in the southern have been at one time or another measure i for parallax. But no one has attempted to measure the parallax of all stars of the third, fourth, fifth, or sixth magnitudes. Astronomers have selected from among these stars those which afford

some striking indication of nearness, such as the great proje motion of 61 Cygni. If, therefore, we take the paraliaarrived at in this manner for comparison, we are comparing to results attained for all stars of the first magnitude with th attained for a small number of exceptional stars of the fifth o sixth.

How far Prof. Eastman's data are otherwise trustworthy Inn not consider. I may refer your readers to a very full list of paraxalles hithe to determined, published by Mr. Herbert Sadler in the February number of Knowledge, by which it will appe how discordant and untrustworthy these results are. But exceptional character of Prof. Eastinan's faint stars is sufficiently evident from the table itself. His first group, with mean mag tude 5'57, has a mean proper motion of 4" 9;; the second grou with a mean magnitude 5.59, has a mean proper motion 201 Surely Prof. Eastman does not mean that the average proper motion of stars of the magnitude 5.58 is 3" 63. There is L one star in a hundred of this degree of faintness which posse such a proper motion as this. W. H. S. MONCK. Dublin, February 15.

P.S.-It is possible that a sphere enclosing the thirty neares stars to us would include more faint stars than bright ones; ta I think it certain that it would not include as large a percen ig: of fifth magnitude stars as of first magnitude stars. The fr magnitude stars do not exceed twenty, and a few of them sera to be very distant. The fifth magnitude stars are reckoned hundreds, and a few of them are comparatively near.

The Longevity of Textural Elements, particularly in Dentine and Bone.

WHATEVER views we may take of the theories of Weismann which at present occupy the attention of biologists, they may i hailed as giving new directions to research, and one of the su jects about which his allusions will probably lead to further inquiry is the length of time during which textural elements coo tinue individually. I have used the word longevity at the top of this letter; but, perfectly admitting the justice of Weismana's criticism-that division into two, each of which is a unity like 15c first, is not death-I feel driven to the dire necessity of inven ing a new word, permanunity, to denote permanence without division; and it is of such permanence or longevity of the un divided unit that I wish to note a circumstance which Lu recently presented itself to my mind.

Every anatomist is aware that the living elements of destin are nucleated corpuscles with elongated branches, which air embedded in the matrix, and lengthen as the dentine increase in thickness, while the corpuscles themselves retire inwards, re maining at the boundary of the lessening pulp cavity. The 200 tinuity of the tubes containing these fi res furnishes, as soon one thinks of it, convincing proof that they are the same branches and the same dentine corpuscles which are found when the dentine begins to be deposited and when it is completed But the dentine begins in childhood, and may go on increasing in thickness in old age, with its tubes still continuous, though losing their regularity of position. Therefore, dentine-corpuscles continue alive and without division through the greater part of the life of the organism.

The interest of this is exceedingly great, if the relation of dentine to bone be considered. Bone has a matrix similar to dentine, and has branched corpuscles; but the bone corpuscles differ from the dentine-corpuscles in becoming completely em bedded in the mineralized matrix, without any attempt to retire from it, and thus come to have branches on every side. Under the microscope one can see in compact bony tissue that there is a continual reabsorption and redeposition of bone going on; and these alternating processes are brought about in a way which is easy to understand, though very generally misapprehended. In consequence, probably, of the very pressure exercised by the bony deposit on the corpuscles, the corpuscles are excited to absorb it; and one sees absorption spaces commencing sometime in the centres of haversian systems, and sometimes in individua) lacune. The ac'ivity thus aroused in the corpuscles causes them to enlarge and to attempt proliferation; which being in the first instance modified by their close surroundings leads to their being converted into large multinucleated masses, the so-called giantcells or osteoclasts. But when a greater amount of room has teen obtained, these ma-ses separate up into corpuscles with ore nucleus each, bone-rorpuscles or osteoblasts, which, arraying themselves around the cavity, initiate the formation of new

concentric lamina of bone. Thus it is certain that the permanunity of the bone-corpuscle is very inconsiderable indeed. It may be difficult to define it exactly, but a general consideration of the rapid changes in the shafts of young bones leads me to think it probably much less than a year.

There is thus a very surprising contrast between the undivided persistence or permanunity of a bone-corpuscle and that of a Mentine-corpuscle, which is in various respects so similar to it. While there are numerous instances of very short-lived c rpuscles in the body, I am not aware that until now proof has been offered of the persistence of any living tissue-elements throughout the life of the organism. JOHN CLELAND,

Some Notes on Dr. A. R. Wallace's "Darwinism." I HAVE just read this most interesting work, "Darwinism"seeming to me the clearest and most useful account of the Darwinian theory of evolution ever yet published-and while reading it I have made note of a few matters which I may, perhaps, be allowed t touch on here.

On p 43 are quoted the numbers of varieties of the two snails, He is nemorals and H. hortensis, enumerated by a French author-no doubt Moquin-Tandon. These numbers, however, fall far below those actually known at the present day. These nails vary in many ways, but taking variations of handing alone, I know of 252 varieties of H. nemoralis, and 128 of H. hortensis. To further illustrate the extreme variability of the Mollusca, take the varieties of land and freshwater Mollusca found in the British Islands. Of the 88 species of land shells we have 465 named varieties, and of the 46 species of British freshwater hells are 251 varieties. So that, excluding probable synonymy, we have about 5 named varieties in Britain to every species of aland mollusc.

In the same way, the numbers of Rosa and Rubus quoted on 77 are below the mark. Of Rosa canina, 33 varieties are known in the British Islands, while the British Rubi number 63 sapposed species.

A good example of a species "occupying vacant places in nature" (p. 110), is afforded by the little mollusc Cæcilianella acula, which is simply organized, and lives in great numbers un le ground (vide Naturalist, 1885, p. 321).

The true cause (as it seems to me) of the variability of freshwater species seems hardly indicated on p 110. All freshwater productions, except those inhabiting large river basins (as the Mississippi), present these peculiarities-they are exceedingly variable and plastic, so that we get few but polymorphic species. Now, for the successful spread of freshwater organisms, it is ssary that they should be plastic, to adapt themselves to the new environment of every pond or river, and the varieties thus required must not become fixed species, because it is their very changeability under new environment that makes them successful in the struggle for existence and increase. Freshwater forms migrate more than is commonly supposed, and the contents of any pond or river are ever varying. Hence the necessities I have indicated. These points are exceptionally clear in the se af the Unionide of Europe and North America (see cnce Gosrp, 1888, pp. 182-184).

In

Colorado presents an exception to the rule (p. 112), that two species of Aquilegia are rarely found in the same area. Colorado we have five columbines, viz. A. formosa, A. chrysintha, A. brevistyla, A. cærulea, and A. canadensis. But A. rulea is the only one that can be called abundant.

On p. 139, it is stated that specific characters are essentially ymmetrical. Yet the ocelli and spots on the butterflies of the families Satyridae and Lycanidæ surely afford specific characters, and they are frequently asymmetrical (see Entomologist, 1889,

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On p. 151, we are told that in Ireland hardly one of the land molluses has undergone the slightest change. This is not quite true, as the following forms seem to be peculiar to Ireland: Auto eter var. fasciata, Geomalacus maculosus vars. allmani, and andrewsi, Limax arborum var. maculata, L. arbarum var. decipiens, Succinea vitrea var. aurea, and S. tiofferi var. rufescens. But these peculiar forms are not more numerous (but less so) than would be found in almost any continents] area of equal size.

The theory (p. 206) that a recent change of food-plant has to do with the presence of green and brown varieties of the rva of Macroglossa stellatarum seems hardly tenable, as so many larvæ of different species and genera vary in the same

mander.

I have thought (Ent. Mo. Mag., 1889, p. 382) that asymmetrical variation in insects occurred most often on the left side. On p. 217 it appears that the same thing occurs in some Vertebrata.

On p. 230 the idea of environment directly influencing the prevalent colours of organisms is put aside as improbable. Yet it has seemed that moisture was the cause of a certain phase of melanism, especially among Lepidoptera. Evidence bearing on this point has been given during the last few years in the Entomologist.

The land shells on the small islands off the coast of Kerry, Ireland, are pale in colour, as I have recorded in Proc. South London Entom. and N.H. Soc. for 1887, pp. 97-98.

The point on p. 233, about the conspicuous colours of the Aculeate Hymenoptera, seems open to question. In temperate regions, at least, the Aculeata are mostly of very dull coloursas the Andrenida, many of the Apide, and hosts of others. Even the brilliant green Agapostemon flies among bright green foliage and yellow flowers, and is not very conspicuous when alive in its native haunts. On the other hand, the non aculeate Chrysidida and Chalcidide are often exceedingly brilliant in colouring.

It seems quite doubtful whether the abundance and wide distribution of Danais archippus (p. 238) is due to immunity from parasites, &c., while its migratory habits are a quite sufficient explanation of the facts. Besides, it has at least one parasitethe Pleromalus archippi.

The "progressive change of colour" (p. 298) is well illustrated by the change from yellow to scarlet exhibited by so many groups of species. Scarlet species nearly always occasionally revert to yellow, and there are generally yellow species in the same genus. For details see Proc. South Lond. Ent. and N. H. Soc. for 1887.

Yellow flowers (see p. 316) seem the most attractive to insects in Colorado, and Mr. F. W. Anderson tells me that the same is the case in Montana. From reasons given in Canadian Entomologist, 1888, p. 176, I am of the opinion that insects cannot distinguish red from yellow.

It has seemed to me (see p. 359) that the agency of wind in distributing insects is greatly exaggerated. I believe whirlwinds may be most important as distributing agents, but ordinary gales less so. Many species of insects migrate, but usually during calms. Also (p. 350) the opinion that insects are often carried to the summits of mountains by winds seems to me without sufficient support. Many species of insects live only or habitually at high altitudes, and their presence there is no proof that they were carried there by winds, especially when they are specifically distinct from the species of lower regions. Plusia gamma, on the summit of Mont Blanc, is not very remarkable, as the moth is a great wanderer, and quite capable of finding its own way to high altitudes. Finally, I believe winds very rarely blow up mountain slopes. I have lived some time at the base of the great Sangre de Cristo Range in Colorado, and although violent winds blow down very frequently, I have never observed an upward wind, and residents whom I have questioned are unanimous in saying that they have never known a strong wind blow up the mountains. And the way the trees are bent and twisted at timber-line (11,500 feet), often with only branches on the side towards the valley, well indicates the direction of the winds.

I think, perhaps, the scarcity of Monocotyledons in the Rocky Mountains (p. 401) as compared with northern regions, is more apparent than real-the difference indicated in the books being due to the fact that the western grasses are not so well known as the eastern ones. Ferns are rarer on continents than on islands, and the dryness of the Rocky Mountain region is unfavourable to them.

A good instance of the effect of environment (see p. 419) recently came under my notice. The polymorphic snail Helix nemoralis was introduced from Europe into Lexington, Virginia, a few years ago. Under the new conditions it varied more than I have ever known it to do elsewhere, and up to the present date 125 varieties have been discovered there. Of these, no less than 67 are new, and unknown in Europe, the native country of the species! The variation is in the direction of divi-ion of the bands. An incomplete list of these varieties is given in Nautilus, 1889, pp. 73-77.

It seems doubtful (see p. 433) how far prickles are a protection from snails and slugs. I found prickles in the stomach of Parmacella (a slug), as recorded in Journal of Conchology, 1886, pp. 26-27.

It is a minor matter, but it seems a pity that the nomenclature of the species in a standard work like "Darwinism" should not be scrupulously exact. Thus (p. 17), "Phalana" graminis should be Charwas graminis. "Helisonia" (p. 44) should be Helisoma, and it is only a section, or subgenus, of Planorbis. On p. 235, "filipendula" and "jacobea" should read filipendula and jacobea. Sphinx fuciformis," of Smith and Abbott (p. 203), is really Hemaris diffinis, while on p. 204, Sphinx tersa is a Charocampa, and " Sphinx pampinatrix" is Ampelophaga myron.

66

66

T. D. A. Cockerell,

West Cliff, Custer Co., Colorado, January 22.

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A Formula in the "Theory of Least Squares." SOME time ago, having had occasion to investigate the relation between (2) and (2) in the "Theory of Least Squares,' I found a simple formula which connects them, and which I have never seen given in any of the text-books on the subject. I inclose it, and hope it is worth publishing in your journal. University of Toronto, February 1. W. J. LOUDON.

Let a number of observations be made on a quantity whose true value is T. If these observations be represented by M1, M2, M3, M, then the most probable value is A, the arith(M). If, moreover, the true errors be

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IN Prof. Moseley's account of his visit to the Cape of Goo, Hope ("Notes of a Naturalist on the Challenger," p. 153, following sentence occurs :-" Again, there are tracks of the Ichneumon (Herpestes), called by some name sounding li 'moose haunt."""

In Todd's "Johnson's Dictionary," 1827, we find : "* Mou hunt, a kind of weasel ;' two quotations being given:-) "You have been a mouse-hunt in your time" ("Romeo 2 Juliet," iv. 4). (2) "The ferrets and mouse-hunts of an index (Milton, "Of Ref. in Engl.," B. 1).

Halliwell's "Dictionary of Archaic and Provincial Words (1847) gives, on p. 564: "Mouse hound, East. A wessel Halliwell denies the identity of this word with Shakespeare's mouse-hunt; and Nares ("Glossary ") inclines to a similar view But in any case it seems clear that Prof. Moseley's moose haunt is a dialectical English form-mouse-hunt or mouse hound; a general word for weasel." E. B. TITCHENER 3 Museum Terrace, Oxford, February 17.

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The Chaffinch.

THE chaffinch sings almost throughout the year in this locality. The male bird never leaves us in winter like the female, ani I can be seen in large flocks daily. A singular circumstance the occurred here in December 1888 with regard to a chaffir、a may be of interest. At one o'clock in the morning, during gale, a chaffinch tapped at my study window. On this being opened, it flew into the room and roosted on a bookshelf; nex morning it was liberated. This was repeated on two subsequen gales. Not only did it sing each time on being liberated, E. all through the winter and spring it followed me about *** garden, singing. E. J. LOWE Shirenewton Hall, near Chepstow, February 11.

ON THE NUMBER OF DUST PARTICLES 1 THE ATMOSPHERE OF CERTAIN PLACESİN GREAT BRITAIN AND ON THE CONTINENT WITH REMARKS ON THE RELATION BE TWEEN THE AMOUNT OF DUST AND METEOROLOGICAL PHENOMENA.

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HE portable dust-counting apparatus, with which the observations given in the paper were taken, was shown to the meeting. The apparatus, which was de scribed in a previous communication to the Society, 5 small and light. It is carried in a small sling-case measuring 8 × 5 × 3 inches. The stand on which it is supported when in use packs up, and forms, when capped with india-rubber ends, a handy walking stick, 1 inch 7 diameter and 3 feet long. No alterations have been made in the original design, and the silver mirrors which at first gave trouble and required frequent polishings, have beer. used every day for two or three weeks without requiring to be polished, when working in fairly pure country air.

With the paper is given a table containing the results of more than two hundred tests made with the apparatus. In addition to the number of dust particles there's entered in the table the temperature and humidity of the air, the direction and force of the wind, and the trans parency of the air at the time.

The first series of observations were made at Hyères... small town in the south of France, situated about 2 miles from the Mediterranean. The observations were made on the top of Finouillet, a hill about 1000 feet high. The number of particles on different days varied here from 3550 per c.c. to 25,000 per c.c., the latter number being observed when the wind was blowing direct from Toulon which is distant about 9 miles.

Cannes was the next station, the observations being Abstract of Paper read before the Royal Society of Edinburgh February 3. Communicated by permission of the Council of the Society

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