54 



KNOWLEDGE. 



February, 1915. 



vears 1S45, 1S55, 1SS6, and coldest of all in 1S95. It was 

 a very mild month in the years 1850, 1867, 1869, 1872, 

 1S77, 1903, and 1914. 



The average mean temperature at Greenwich for Feb- 

 ruaiy is 39° -5 ; in 1869 it was as high as 45° -6, while in 

 1895 it was as low as 29°-l. The average maximum tem- 

 perature is 45° -2 ; the highest mean was 51°-8, in 1869, 

 and the lowest 35° -2, in 1895. The average minimum 

 temperature is 34° -3 ; the liighest mean was 39° -7, in 1869, 

 and the lowest 22° -8, in 1895. The absolute highest tem- 

 perature recorded w-as 63°-9, in 1899, on the 10th, and 

 the absolute lowest 6° -9, in 1895, on the 8th. The average 

 number of days on which tlie temperature falls to or below 

 the freezing-point is ten. In 1895 the temperature was 

 continuously below the freezing-point for seven days, 

 from the 5th to the 1 1th. 



The average rainfall for the month of February is 1 •52-in. ; 

 the greatest amount was 4-03-in., in 1866, and the least 

 0-04-in., in 1821. The heaviest fall in one day was 2-89-in., 

 in 1831, on the 7th. The average number of " rain days " 

 {i.e., on which 0-01-in. fell) is 12-4 ; the greatest number of 

 days was twenty-two, in 1893. and the least three, in 1857. 

 Snow falls on the average on three days. The average 

 amount of bright sunshine in the City of London is thirty- 

 one hours, but at Kew Observatory, Richmond, the amount 

 is fifty-six hours. 



The average barometric pressure for February is 

 29-972-in. ; the highest mean was 30-473-in., in 1891, 

 and the lowest mean was 29-499-in., in 1776. There is 

 thus, in the neighbourhood of London, a variation of nearly 

 an inch in the monthly nieans. The highest recorded read- 

 ing in the British Isles was 31-007-in. at Gordon Castle, 

 Banff, in 1808, on the 24th. 



From a discussion of the results of the observations in 

 England and Wales during the thirty years 1881-1910 it 

 appears that when the barometric pressure is high in 

 February it is usuallv followed by low pressure in March, 

 and vice versa ; and that a wet Februarj' is usually followed 

 by a dry March. 



" If Candlemas Day * be fair and bright, 

 Winter will have another flight ; 

 But if Candlemas Day bring clouds and rain, 

 Winter is gone and won't come again." 



* February 2nd. 



RELATIVE HUMIDITY IN ENGLAND AND WALES. 

 — At the December meeting of the Royal Meteorological 

 Society Mr. W. F. Stacey read a paper on " The Distribution 

 of Relative Humidity in England and Wales." He had 

 prepared mean monthly and annual maps of relative 

 humidity based on the 9 a.m. dry and wet bulb thermometer 

 obser\-ations made at over ninety stations during the ten 

 years 1901-10. An examination of the maps shows that 

 in winter the air over the interior of the country is more 

 moist than that over the coastal regions ; that the minimum 

 relative humidity occurs earlier in the year in the western 

 parts of the country than in the eastern ; that in summer 

 the air over the interior of the country is drier than that 

 over the coastal regions ; and that the smallest range of 

 humidity is found in the west and the greatest in the 

 interior towards the east. The distribution of temperature 

 is the chief determining factor in the distribution of relative 

 humidity ; while sea influence, the direction and character 

 of prevailing winds, the configuration of the country, all 

 have important effects on temperature, and therefore on 

 relative humidity. 



MICROSCOPY. 



By J. E. Barnard, F.R.M.S. 



THE MICROSCOPE AND THE WAR.— That there is 

 any connection between the microscope and the present 

 disastrous European War is not immediately apparent. 

 A little deliberation, however, will show that both the use 

 and the production of microscopes commercially are seriously 

 affected. If we consider the matter from the point of 



view of production, it is quite clear that the number of 

 instruments available at the present moment is not so great 

 as formerly. A very large number were previously imported 

 from the Continent — principally from German^' — and these 

 are not now obtainable. On the other hand, the use of the 

 instrument has been restricted, so that the demand in 

 general is not so great. British manufacturers have no 

 doubt, to some extent at least, stepped into the breach, 

 and are producing to the utmost of their capacity. This, 

 however, does not mean very much, as nearly all manu- 

 facturing opticians are fully occupied in making optical 

 instruments of various sorts for Ann}- purposes. In some 

 respects the position of the microscope industry is analogous 

 to the anilme dye trade. The microscope in its earlier days 

 was almost entirely a British production, whereas it has, to 

 a large extent, especially on its optical side, passed into the 

 hands of Continental makers. If we read through the earlier 

 numbers of The Journal of the Royal Microscopical Society, 

 it is evident that about thirtj^ to forty years ago, when the 

 microscope was in course of development, British makers 

 were in the very front rank. The influence of their design 

 and method of construction is still largely felt ; in fact, it 

 is not too much to say that at the present time, if a micro- 

 scope of the very finest construction is wanted, it is still 

 possible, and perhaps even advisable, to get one of British 

 manufacture. One of the features of the Continental 

 instrument has been its simplicity ; and in this respect there 

 is something to be said for it ; but in evol\-ing such a type. 

 Continental makers have striven more for cheapness than 

 to provide an instrument that is thoroughly efficient. If 

 we take the outstanding characteristic, for instance, of the 

 Continental stand, the horseshoe foot, we are at once con- 

 fronted with a design which has nothing much to recom- 

 mend it ; whereas the British type of tripod foot is in every 

 respect more stable, and a better method of support in 

 whatever position the instrument may be used. 



The sub-stage, which is now recognised as of primary 

 importance, the Continental makers have reduced to its 

 simplest proportions, and in some respects have made it 

 almost a useless feature of the instrument owing to the lack 

 of centring adjustment. The British manufacturers have 

 never been behindhand in this particular, and their instru- 

 ments of the better class have been such that one might use 

 them for the most exacting work. 



That most of the improvements in microscope design 

 have been of British origin is a matter of common know- 

 ledge, and it is only necessary to consult the earlier Uterature 

 of the subject to realise this. It is hoped, therefore, that 

 British makers will not lose the opportunity that has pre- 

 sented itself, of recovering at least a large part of the trade 

 that they have lost, and that they will set themselves to so 

 deal with the matter that when competition arises again 

 there will be real strength behind it to meet every possible 

 contingenc}'. That the Continental makers, particularly 

 those of Germany, have not relied on cheap labour, but on 

 specialisation and systematic methods of production, is 

 beyond question ; and unless the British makers are pre- 

 pared to launch out and do their part in this direction there 

 is perhaps little hope for them in the future. So far as the 

 optical side is concerned. Continental makers have been 

 very much to the fore. It is no uncommon thing for a 

 microscope of best British design and manufacture to be 

 fitted with objectives of Continental make, and that, not 

 because they are cheaper, but rather because they are better 

 in quality, the price in some cases being substantially 

 higlier than those of British origin. In this respect it is 

 somewhat reassuring to know that at least two British 

 firms are making a feature of apochromatic objectives, and 

 there is little doubt that these will be in eveiy respect 

 equal to those from the Continent. When the apochromatic 

 objective was first brought out there was a very definite 

 distinction between it and the achromatic object which 

 had been in general use up to that time. Even now the 

 difference between the true apochromatic objective and 

 the ordinary objective is a fundamental one, although 

 there are many objectives which do to some extent bridge 



