The variations of the field strength with pressure of the gas seem to agree with the Grotthuss chain hypothesis as far as the measurements go.

Upon the assumption that the passage of electricity from a point to a plate is a one-way flow, it is possible to obtain a value of the ratio of mass moving to electricity carried by it (i.e., the electro-chemical equivalent of the discharged matter) in terms of the slopes of potential and pressure brought about by the discharge, and the density of the current passing. Experiments are now in progress to determine this ratio, if possible. So far they point to a number far in excess of the electrolytic value. This may be due to error in the measurements, or, possibly, to the presence of metal dust in the discharge.

Measurements, also still in progress, have been made on the mechanical forces which act on a point during discharge. They point to interesting differences between + and electricity, and it is hoped that useful information may be obtained as to the manner in which the two electricities leave the point by further work in this direction. Your Committee asks for reappointment with a grant of 501.

Report of the Committee, consisting of Lord MCLAREN (Chairman), Professor CRUM BROWN (Secretary), Mr. MILNE HOME, Dr. JOHN MURRAY, Dr. BUCHAN, and the Hon. RALPH ABERCROMBY, appointed for the purpose of co-operating with the Scottish Meteorological Society in making Meteorological Observations on Ben Nevis.

DURING 1890 the hourly observations by night and by day at the Ben Nevis Observatory have been carried on uninterruptedly by Mr. Omond and the assistants, and as heretofore the five daily observations at Fort William have been made with great regularity by Mr. Livingston. As intimated in last report, a vitally important advance was made in the system of observations on Ben Nevis by the opening of the low-level observatory in Fort William on July 14, 1890, for regular continuous observations. This observatory has been equipped by the Meteorological Council with a complete set of self-recording instruments, such as are in use at the first-class observatories of the Council. The directors have thus now at their disposal the best information available for extending the scientific and practical inquiries they have undertaken through the unique facilities offered by these well-equipped observatories. A beginning has also been made with an elaborate discussion of this double series of hourly observations of which some account will be given in this report.

The directors were again able to give relief to the various members of the observing staff by the courtesy of the following gentlemen, who have given their services as observers for periods varying from four to eight weeks:-Messrs. R. C. Mossman, James McDonald, M.A., and Alexander Drysdale, M.A., B.Sc.; and Messrs. P. Gillies and C. Stewart, from Professor Tait's Laboratory, are now (August, 1891) assisting in the work of observing.

For the year 1890 the following were the monthly mean pressures and temperatures, hours of sunshine, amounts of rainfall, and number of fair

days, or days of less than 0.01 inch of rain, at the observatory, the mean pressures at the Ben Nevis Observatory being reduced to 32° only, while those at Fort William are reduced to 32° and sea-level :

Feb. March April May June July Aug. Sept. Oct. Nov. Dec. Year

Mean Pressure in Inches.

Ben Nevis Ob- | 24.983] 25.543 25-079 25-226] 25·316′ 25-349] 25-297] 25-312) 25-482| 25-395 25-147) 25-409 25-295 servatory

Fort William

Difference

29-548 30-221′ 29-674 29-820 29-845 29-878 29-802 29-799 29-964 29.955 29-732 30-084 29-860 4-565 4.678 4.595 4.594 4:529 4:529 4:505 4487 4:482 4:560 4:585 4675 4:565

At Fort William the mean temperature of the year was 47°.7, being 0°.5 above the mean. The exceptional departures from the monthly means were : January 28, May 3°.2, September 31, and October 20 above, and July 20.3, August 3°.1, and December 2°-4 under, the means. The mean annual temperature at the top of the Ben was 31°.3, or 0°4 above the mean, and as contrasted with Fort William the departures from the means were in July 20.8 and in August 1°.0 under and in September 400 above it. In anticyclonic weather, such as largely prevailed in September, the excess of temperature at the top of the Ben is always relatively higher than at sea-level adjoining.

The minimum temperature for the year was 9°.0 on December 19, being about the point to which the temperature has fallen each year since the observatory was opened. The maximum was 58°.9 on September 7. This is about the lowest annual maximum temperature hitherto observed, and it is otherwise remarkable as having occurred so late in the season. Indeed, low temperatures ruled during the summer in an unusual degree, the highest in June being 45°-6, July 51°7, and August 53°-7. Thus the extreme range of temperature for the year was 49°.9; in the previous year it was 55°.4.

The registration of the sunshine-recorder showed only 591 hours out of a possible 4,470 hours. Excepting 1886, when the number was 576,

this is the lowest since the observations began. In January only 4 hours were registered, being the lowest monthly amount yet observed, but in December the number of hours was 22, being considerably in excess of the hours registered at stations generally over the United Kingdom during this exceptional month.

The rainfall was the heaviest yet recorded in any year, being 198.34 inches, and if the amount were calculated for the meteorological year beginning with December, 1889, the annual amount would be 213-63 inches. The rainfall for October, 37.30 inches, is the highest yet recorded in any month; and 29-42 inches were recorded in January and 27-31 inches in March. On October 3 the rainfall was 7.29 inches, but for the 24 hours from 9 P.M. of the 2nd to 9 P.M. of the 3rd the extraordinary quantity of 8.07 inches was collected. In four months the rainfall was the highest yet recorded for these months.

The number of days on which the rainfall was nil, or less than the hundredth of an inch, was 83, being the fewest number of fair days of any year since the observatory was opened. There were 17 fair days in February, 15 in April and December, but none in January. There were 66 days on which one inch or upwards fell. In October there were 15 such days and 11 in January.

The rainfall of 1890 in the eastern part of Scotland to the south of the Grampians was nearly everywhere under the average, the deficiency being a sixth in the Border Counties. On the other hand, in north-western districts it was about a fifth above the average. The annual average at the observatory since 1885 is 134.50 inches, and hence the rainfall of 1890 was 63.84 inches, or 48 per cent., above the average-an excess nowhere approached at any observing station in Scotland.

Atmospheric pressure at Fort William was 29.860 inches, or 0.032 inch above the mean pressure. The monthly extremes were the minimum in January and the maximum in February, these being respectively 0-229 inch below and 0.295 inch above the means of these months.

The following shows the departures from the means of the pressure and rainfall of the four months of heaviest rainfall at the Ben Nevis Observatory:

Differences from the Means.

On

It will be observed that during the two last months, when the rainfall was greatly above the average, pressure also was above the average. the top of the Ben it repeatedly occurs that high pressures are accompanied with very heavy and long-continued rains.

Considerable progress has been made during the year with the discussion of the Ben Nevis observations.

An exhaustive examination of the Winds of Ben Nevis,' by Messrs. Omond and Rankin, has been recently completed and the results communicated in a paper read before the Royal Society of Edinburgh. The authors show that while the sea-level winds in this part of Scotland are, with respect to the distribution of pressure, in accordance with Buys Ballot's Law of the Winds, the Ben Nevis winds do not at all fit in with

such a distribution of pressure, but that on the contrary they point to a widely different distribution of pressure at the height of the observatory, 4,407 feet above the sea. In large storms, with a deep barometric depression in the centre, the Ben Nevis winds are practically the same as at lower levels; but with smaller storms great differences are presented. In these cases it is remarkable that with a cyclone covering Scotland, the North Sea, and Southern Norway the winds frequently blow, not in accordance with the sea-level, isobars, but in an entirely opposite direction, suggesting an outflow from the cyclone towards the anticyclone near at the time on the other side. It is further remarkable that this outflowing seldom or never occurs when the centre of the storm is to the south or west, but only when it lies to the north or east. If the wind on the hilltop is not at a right, or greater, angle from the sea-level wind, it is usually nearly the same as it; the supposed veering of the wind at great heights required by the theory that a cyclone is a whirling column, drawing the air in spirally below and pouring it out spirally above, is so seldom observed as to be the exception, and not the rule. important result and the analogous observation that frequently in great storms of winds prostrated trees lie practically in one direction over wide regions show impressively how much observation has yet to contribute before any satisfactory theory of storms can be propounded.

This

The winds of other high-level European observatories, which may all be regarded as situated in anticyclonic regions, have been examined, and it is found that they show the closest agreement with the winds at low levels in the same regions. This result separates the Ben Nevis Observatory from other observatories, so as to form a class by itself, the differentiating cause being the circumstance that Ben Nevis alone lies in the central track of the European cyclones. This consideration emphasises the value of the Ben Nevis observations in all discussions of weather. It may be added that, with respect to the relation of the winds to the lowlevel isobars, Ben Nevis Observatory is more pronouncedly a high-level observatory in winter than in summer, or, more generally, in cold than in warm weather.

Mr. Rankin has communicated to the directors a paper on the results of the dust-counting observations of the past year. The highest number observed was 14,400 per cubic centimetre in April last, whilst the lowest, 0, was observed in July, 1890, and again in March, 1891; and here it must be noted that each observation is really the mean of ten observations taken at the time. The greatest amount of dust is observed when the wind is E., S.E., or S., both at sea-level and the top of the Ben; but when the winds at the top diverge most from those at sea-level then the lowest dust values are obtained. We have here, broadly indicated, another contribution to weather prognosis afforded by the dust observations, since they point to quite different phases of weather.

True fogs and wet mists exhibit marked differences. In fog there is usually a considerable amount of dust; in mist, or wet mist, usually very little. It is observed when the number of dust particles noted is extremely small, or even 0, that the air is surcharged with aqueous vapour, if such a condition be supposed possible, and that then, there being no dust particles to serve as nuclei on which the vapour might condense, it simply condenses on all exposed objects direct from the air. This has been found to be the most wetting condition of the air, a few minutes only being sufficient to give the observer a thorough soaking. Every

post and rope seem running over with water, though, looking out at the weather, one has no idea it is nearly so wet.

Sufficient observations have been made to show a well-marked diurnal variation in the numbers of dust particles. The following are the trihourly results for March, April, and May, 1891:—

The daily minimum thus occurs when the daily strength of the wind is greatest, and also the descending current, down the mountain, and the maximum when the wind is least strong and the ascending current up the mountain strongest.

Mr. R. C. Mossman has communicated a paper to the Scottish Meteorological Society on the cases of silver thaw at the Observatory, which will appear in next issue of the Society's Journal. From 1885 to 1890 there occurred 198 cases, lasting in all 873 hours-that is, cases in which rain froze as it fell. The maximum frequency is from November to March. It occasions, as may well be supposed, much inconvenience and discomfort to the observers.

The chief point established by Mr. Mossman is that the distribution of pressure over Western Europe is at the time always substantially the same. The daily weather charts show that on these 198 days the distribution of pressure was for the Ben cyclonic on 137 and anticyclonic on 61 days. In anticylonic cases a cyclone is off the north-west coast of Norway, while the anticyclone stretches away over the south of England and Ireland. In cyclonic cases Ben Nevis is clearly within the area of low pressure, the centre of which again is off the north-west coast of Norway, while the anticyclone is removed farther to southward over the Peninsula. Hence the value of this phenomenon in forecasting weather. The average duration is 6 hours in winter and 3 in summer. The longest continued was 41 hours on January 3-4, 1889. The lowest temperature at which it has occurred was 18° 0, but nearly in all cases the occurrence takes place shortly before a thaw.

During the past year the unremitting attention of Dr. Buchan has been given to the examination and discussion of the hourly observations of the two observatories. The discussion includes the ten months ending May, 1891.

In entering on the discussion it quickly became apparent that the influence of high winds on the barometer was the first inquiry calling for serious attention. The depression of the barometer during high winds was plainly so serious as to render the examination of many questions all but a hopeless task until some approximation was made to the values of these depressions for different wind velocities.

Fortunately the two observatories present the conditions favourable for this investigation. They are so near to each other as to form virtually but one observatory, the barometer at the top being in a building exposed to winds of all velocities up to at least 150 miles an hour, whereas the other barometer is in a sheltered building, where light winds prevail