April 27, 1893] 



NA TURE 



62 



illness. Prof. Cayley also contributes some tables of pure 

 reciprocants to the weight S (pp. 75-77)- Two short notes 

 follow on the differential equation, Au + k-u^o by Maxime 

 Bocher (pp. 78-83), and geometrical illustrations of some 

 theorems in number by Ellery W. Davis (pp. 84-90, with a 

 diagram). M. Halphen is the mathematician whose portrait is 

 given with this opening number. 



Bulletin dc V Academic Koyale de Belaiqtie, No. 3 (1893).— 

 Amongthe scientificpapers communicated to the Academy are the 

 following : On the common cause of surface tension and evapor- 

 ation of liquids, by G. Van der Mensbrugghe. The author 

 deduces from his theory an explanation of the fact that evapor- 

 ation is more rapid from a convex, and less rapid from a con- 

 cave, than from a plane surface. — Survival after the successive 

 section of the two vagi, by M. C. Vanlair. Survival after 

 successive section of both the branches of the vagus nerve can 

 be obtained in full-grown animals as well as in young ones. 

 The time necessary for the regeneration of its inferior laryngean 

 branch is generally much longer than that hitherto accepted. 

 In the full-grown dog the period exceeds at least ten mouths. 

 The regeneration of one branch is quite independent of the 

 section of the other. The question whether the pneumogastric, 

 like the sciatic nerve, possesses the power of regenerating itself 

 twice in succession remains as yet unanswered. It is, however, 

 certain that an interval of six months and a half does not suffice 

 for its second regeneration. — On the digestion of the coelen- 

 terata, by Marcelin Chapeaux. The action of the ferments 

 secreted by the actinia upon starch, cellulose, chlorophyll, and 

 fat, was investigated. Starch submitted to the action of an 

 aqueous solution of these ferments, or injected into the gastro- 

 vascular cavity, was transformed into glucose. The action was 

 slow in the case of non-hydrated starch. The transformation 

 took place equally well in acid and in alkaline solutions. 

 Cellulose and chlorophyll were not digested. The fats were 

 emulsioned by the ferments contained in the endodermic 

 cellules. These ferments were without effect upon the alga;. 

 Among the Siphonophora digestion is certainly exclusively 

 intracellular. No dissociation of fibrine is, on the other hand, 

 ever observed in the gastrovascular cavity, and no difference 

 could be established between the alkalinity of the liquid con- 

 tained in this cavity and the surrounding sea-water. — Contri- 

 bution to the nitrogen question, by A. Petermann. This is an 1 

 experimental confirmation of the results of MM. Schloesing fils 

 and Laurent, showing that free nitrogen is absorbed from the air 

 by the micro-organisms of the soil. 



SOCIE TIES AND A CADE MIES. 

 London. 



Royal Society, March 2. — " Harmonic Analysis of Hourly 

 Observations of Air Temperature and Pressure at British 

 Observatories," by Lieut. -General R. Strachey, R.E., F.R.S. 



This paper is a discussion of the results of the computations 

 contained in a volume recently published by the Meteorological 

 Office.ofthe harmonic components of the first four orders, for each 

 month for twenty years, of the daily curves of temperature and 

 pressure at Greenwich ; and for the first three orders, for the 

 temperature and pressure, for each month for twelve years, at 

 the seven observatories maintained by the Meteorological 

 Office. 



This system of analysis supplies the means of establishing an 

 exact comparison between various unsymmetrical curves, such as 

 those representing hourly values of temperature, by resolving 

 them into symmetrical components, having periods of twenty- 

 four hours, twelve hours, eight hours, and six hours, and so 

 forth, and its application to the records dealt with in the tables 

 contained in the volume above referred to gives satisfactory 

 proof of the important light it can bring to bear on the periodical 

 changes of diurnal temperature. 



In the usual expression the coefficients of the cosines of the 

 arcs are designated by the letter/, and those of the sines by q. 

 The total amplitude of the component is designated by P. 



A modification of the usual notation is made by the introduc- 

 tion of the value of the epoch of the first maximum that occurs 

 after midnight, which is designated by the letter /<, and estab- 

 lishes the connexion of the component with the hour of the day 

 and the sun's place more conveniently than the method usually 

 adopted. 



NO. 



1226, VOL. 47] 



I. Greemvich Temperature, 



The examination of the tables shows that, with very consider- 

 able variations of absolute magnitude, there is on the whole 

 very marked consistency in the main characteristics of the 

 components. 



Taking as a test the position of the epoch of maximum, which 

 is more directly dependent on the sun's action and on his posi- 

 tion than the amplitude, it will be seen that the values of ^ 

 indicate very clearly the closeness of this connexion. 



In all the components a truly periodical variation of the value 

 of /x is apparent, and the period of maximum always travels 

 backwards, that is, it becomes earlier as the year passes from 

 winter to summer, while it returns in the opposite direction in 

 the change back to winter. 



For the first component the variation of the five years' mean 

 of yu from the twenty years is in no month more than 2^^", or ten 

 minutes of time, and the average for all months is less than half 

 that amount. 



In the second component the variation of the five-year mean 

 from the twenty-year mean is in no month more than 6°, and 

 the average is only 2°'3, or nine minutes of time. 



In the third component the variation of the five-year from the 

 twenty-year mean in no month exceeds 5°, and the average in 

 all months is only 2°'l, or %\ minutes of time. 



The largest variation of the five-year mean of the fourth com- 

 ponent for any month from the twenty year mean is 10°, and the 

 average for all months is 4° -3, or seventeen minutes. Consider- 

 ing huw small are the absolute values of the coefficients p^ and 

 ^4, on which the value of ^14 depends, the average being a little 

 less than tV'^ of a degree Fahrenheit, it is rather a matter of 

 surprise that the variations should be so small than that they 

 should reach their actual amounts. 



The component of the first order, which in the winter is more 

 than double the magnitude of any of the others, and in summer 

 more than ten times as great, gives the dominant character to 

 the daily curves of temperature. In the series of twenty years 

 variations in different years of as much as 100 per cent, are to be 

 found for almost every month, but for the most part even these 

 irregularities disappear in the mean of a series of five years, 

 and the monthly means for the twenty years are remarkably 

 consistent. 



The progression of the value of P, in the course of the year, 

 follows approximately the sine of the sun's meridional altitude 

 and the empirical formula 



P = 10 cos z-o*9i 



gives a close approximation to the values shown in the tables, if 

 a "lagging" of eight or ten days is allowed in reckoning the 

 sun's place. 



The second component has two clearly marked wajcma about 

 the time of the equinoxes, and a principal minimum at mid- 

 summer. 



The component of the third order varies in a converse 

 manner, having two well-marked minima at the equinoxes, with 

 a principal maximum at midsummer. 



The component of the fourth order appears to combine the 

 characters of the two previous ones, having two maxima about 

 the time of the equinoxes, and a principal minimum in the 

 winter. 



The mean value of /n for the first component is 214", corre- 

 sponding to 2h. 26m. p.m., the variation due to season being 

 12° or 48111. of time, by which the maximum is earlier in summer 

 than in winter. 



In the second order the first maximum in June is 24^, or ih. 

 20m. earlier than in January. 



In the third order the difference in the s.\me direction is (>'^, 

 or 4h. 12m. of time. 



In the fourth order there is some doubt as to the manner in 

 which the change of epoch of the summer and winter maxima is 

 brought about. But remembering that the fourth component in- 

 cludes four series of undulations, the most probable explanation of 

 these changes is to be found in a change of the position of these 

 undulati ns, during which, between January and February, when 

 the first maximum is about 10° after midnight, or oh. 4001. a.m., 

 the first recedes, and its place is taken by the second, which 

 leads to sudden appearance of a maximum about 60°, or 4 a.m. 

 A similar change between Octoher and November in an 

 opposite direction would reproduce the maximum at 10° after 

 midnight. 



