348 



NATURE 



[jANUAk 



1 I 



H^l 



LETTERS TO THE EDITOR. 



[The Editor does twt 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 o/ Nature. 

 .Vo notice is lakcu of anonyttwus communications.] 



The Weather of xgtz. 



I iiAVK received the subjoined letters from Dr, Srhmauss 

 at Munich, which may be of interest to your readers. In 

 Kngland in I)eceml>er, 191 1, the temperatures up to 8 km. 

 \v«>re decidedly below the mean. This is nearly always the 

 case in stormy weather. 



In the following table the correlation between the general 

 drift of the atmosphere and the temp«.'rature is shown. 



N denotes the north compt)nent of the drift of the 

 balloon, the positive direction bfiti^ th>- north. 



E, the drift to the east. 



T„ the surface temperature. 



T«, the temperature at a height of 4 km. 



T„ the temperature at a height of 8 km. 



Hj the height of the coirmenccment of the isothermal 

 column. 



The observations in England were taken during the 

 four years 1908 to 191 1 on some eighty different days. 

 Owing to the practice of the International Commission of 

 nearly always fixing the week for daily ascents in the 

 summer, the preponderance of the observations lies in the 

 summer. Since observations made at neighlwuring 

 stations on the same day cannot be considered independent, 

 and since large groups of observations are concentrated 

 into particular weeks, during some of which unusual con- 

 ditions prevailed, the probable errors are really far larger 

 than the number of observations would indicate. 



Correlation Coefficients. 



It will be seen that the only correlation coefficients large 

 enough to be significant are those showing the connection 

 between the height of the isothermal and the temperatures. 



Dr. Shaw's hope, expressed in your issue of December 

 a I, 19 n, seems to be fulfilled, for were there any close and 

 systematic connection between the temperatures and the 

 direction of the air currents, or between the latter and the 

 height of the isothermal, it could scarcely fail to appear in 

 the figures. The small values of the coefficients (0-31, with 

 a probable error of o-i, even if we treat all the observa- 

 tions as independent, is the largest) and the want of agree- 

 ment between the different groups both lead to the 

 conclusion that there is no connection, or at the best a 

 very slight one. 



The connection between the height of the isothermal and 

 the temperature of the air below down to 4 km., and 

 perhaps even to the surface, is very plainly shown, and 

 makes me regret my somewhat rash statement that the 

 surface temperature was more dependent upon the direction 

 of the wind than upon anything else. 



The negative value of — o-i6 between T, and N is 

 certainly curious, and the sign would probably be reversed 

 if there were some hundreds of observations instead of 

 forty-six ; but the drift of the balloon is not necessarily 

 the same as the direction of the surface wind, although, as 

 a general rule, especially when the wind is strong, the 

 two agree fairly well. The negative sign indicates that a 



NO. 2202, VOL. 88] 



Kouth wind !• colder than a north, and must be t<^<^ 

 warning not to aKtibe any significance to small 

 rwflicients. ^^ " 



December 30, 191 1. 



Kgl. bayer. metcv .., . ;; .,, 



Mitnchen, den 11 Uezember, 1911. 4 



Ks wird .Sie im Anschlussc an Ihre Mitteilunii 11 



Natuke 88 S. 175 intere»«ieren zu horcn, dass \ 



Septembcr-fahrten iiber .Miinchen nahezu die gl' 



Verhiiltnissf- aufweisen wic Ihre britischen Aufstiege. 



Es war die Temperaturabwcichung vom Mittel : — 



516 t a 3 4 5 6 7 8 9 10 II 



+a9 +4'3+»''+4'4+4'3+3'4-»-»*3+«'3+»'»-*-«'4+»'o-V4 



Miinchen, den 37 Detembir, 

 Auch noch die Dezemberaufstiege haben eine ati: 

 .Abwetchung iiber Miim t 'i<n. Es warden die ^ 



der drei Dez«'mberauf littelt und die Abs 



ungen vom Mittel gebild 

 ts war dieselbe : — 



Ini a 3 4 5 6 7 8 9 10 •••^ 



4-3'7 *6'3 +55 +5"o +4"o +4-0 +6-« +57 +3*1 -o*i -3*13 



Der grosse Warmevorrat der Atm'ivnh:ir.. in du 

 Herbste ist darin deutlich ausgesproch 



Sir Euwaru Fry has asked ember 



191 1, p. 244) whether the unusual!) warm weather 

 prevailed in Western Europe last summer extended 

 the whole earth. It is possible to answer in the nega 

 so far as Egypt is concerned, for the temperature here 

 below average from June to September. Indeed, on 

 days London had a higher maximum than Cairo, 

 August 9, Greenwich 100°, Cairo 93°. The result 

 retardation of the cotton harvest by some twenty d.' 

 the first picking. 



As regards the cause of the cooler weather, ther- 

 certain amount of evidence that the amount of solar r.idi 

 tion reaching the lowest stratum of the atmosphen- h< 

 was less than usual, if any faith is to be placed lu tl 

 indications of the black-bulb thermometer in vacuo. Vh 

 phenomenon, of course, may be due either to diminishi 

 solar activity or to locally increased absorption in the upp 

 strata, or to a combination of both. In any case, 

 Edward Fry's original query brings us face to face wi 

 what is probably the ultimate question in meteorolosjy 

 given unit increase of solar radiation, calculate the •:• 

 at the earth's surface. The solution will not be id" : tn 

 for all parts of the earth, and so a small and tempora 

 diminution of radiation may at one place cause increase 

 temperature, while at another the reverse is the case. 



J. I. Craio. 



Giza, Eg_vpt, December 31, 191 1. 



English V. Continental Microscope Stands. 



Referring to the interesting article on the merits 

 English versus Continental Microscope Stands in Nati 

 of December 21, 191 1, I notice that whilst reasons 

 given on both sides for the distinctive peculiarities of 

 respective models, and a general suggestion is made as 

 how the present well-recognised types have come abo 

 curiously enough, no reference has been made to wl 

 seems to me to be the real origin of the most import; 

 differences between the two types — I refer, of course, 

 the substage arrangements as a whole. Why is it 

 the English model provides for the exact centring, i 

 frequently for fine adjustment focussing of the subst- 

 optical system, whilst the Continental model does n 

 Why is it that the Continental models, on the other ha 

 provide rackwork mechanism for moving the 

 diaphragm of the condenser out of centre, with means 

 rotating this whole arrangement — a feature absent in 

 English model? 



These things are clearly the outcome of the differ 

 theories which prevailed at one time in England 

 Germany on the question of microscope illumination, 

 the Continent, it must be remembered, the general reco| 

 tion of the utility of substage condensers dates from 

 time when .^bbe worked out his epoch-making theorj' 



