352 



NA TURE 



[May 20, 1909 



most interesting of these represent Tuscany and the 

 Pontine Marshes, while he made an accurate plan of the 

 town of Imola in the Romagna, of Milan, and other 

 cities. Besides being a topographical he was also an 

 eminent physical geographer and astronomer. He held 

 that the earth was a planet, and denied that it occupied 

 a privileged fmsition in the universe, thus being one of 

 the forerunners of Copernicus. He must also be regarded 

 as the founder of the modern theory of wave motion, and 

 his investigations of the question of currents and of other 

 hydraulic problems are remarkable. He believed that 

 rocks were of sedimentary origin, and that mountains were 

 accumulations of river alluvium. He held, for his time, 

 advanced views on the subject of the Deluge, and as he 

 laid much stress on the influence of erosion he anticipated 

 much of the modern doctrine of valley formation. He 

 did good service for meteorology by his study of winds, 

 and he was one of the pioneers of Alpine exploration. Dr. 

 Oberhummer follows his account of the scientific work of 

 Leonardo by a description of the world and star maps 

 constructed by Albert DUrer. He gives interesting repro- 

 ductions of the work of these artistic and scientific men 

 from the originals in the collections at Windsor, the 

 British Museum, and other places. 



The prospect of a short water supply during the coming 

 summer is predicted by the Rev. F. C. Clutterbuck, of 

 Abingdon, in Symons's Meteorological Magazine for April. 

 Speaking particularly of the Thames Valley, Mr. Clutter- 

 buck bases his prediction on the measurements of a well 

 in the Upper Greensand of which he has a daily record 

 for the last forty years, this well having always been con- 

 sidered a good test as regards water supply. Only on 

 two occasions has the well been so low as it is now, viz. 

 in the autumn of 1898 and in the spring of 1905, which 

 was a year of very short water supply in the Thames 

 Valley. In the si.x; months October-March inclusive, 

 1904-5, the rainfall at Abingdon was 9-24 inches; in 

 1908-9 it was 9-13 inches, almost similar . conditions. 

 Therefore, Mr. Clutterbuck concludes, we may expect the 

 s.ime deficiency this year as was experienced in 1905. In 

 an editorial article on the rainfall of the winter half-year 

 it is pointed out that for England and Wales there was 

 a deficiency of more than one-quarter of the normal rain- 

 fall. The dry autumn may produce an exceptionally good 

 wheat harvest this year, but, (he editor observes, the 

 general dryness of the whole winter half-year cannot fail 

 to cause anxiety as to the yield of wells and the replenish- 

 ment of reservoirs. 



Under the tille of " Biblingraphia Botanica," Messrs. 

 \V. Junk, of Berlin, have issued a classified catalogue of 

 nearly 7000 books, journals, and pamphlets dealing with 

 all branches of botany. 



In the Atti dei Lincci, xviii. (i), 7, Dr. G. Agamennone 

 describes certain remarkable long w-aves that were recorded 

 by the seismographs at Rocca di Papa on the occasion 

 of the recent earthquakes of December 28, 1908, and also 

 in the Calabrian earthquake of -September 8, 1905. The 

 same slow waves were observed at Gottingen in 1905 by 

 Angcnheister. 



In the Annals of Mathcmalics (April), x., 3, Prof. E. B. 

 Wilson gives an exposition of the applications of probability 

 to mechanics. The discussion is presented in the form of 

 an introduction to the study of statistical mechanics. It is 

 illustrated by the consideration of simple examples, and 

 well shows how " mean value " and probability for a 

 continuous function depend on the distribution, or, in other 

 NO. 2064, VOL. So] 



words, on the variable with respect to which the function 

 is assumed to be uniformly distributed. 



Messrs. W. Cramp and B. Hovle, in a paper on the 

 electric discharge and the production of nitric acid by 

 I means of it, which appears in the April number of the 

 Journal of the Institution of Electrical Engineers, give a 

 ri'sumi of the various methods which have been used in 

 the attempt to produce nitric acid direct from the nitrogen 

 of the atmosphere, and criticise them in the light of their 

 own researches. They have investigated the relative 

 efficiencies of various forms of electric discharge, and of 

 different methods of introducing and withdrawing the 

 gases, and have found that a considerable number of the 

 results obtained are in agreement with the ionisation 

 theory. It is unfortunate that the authors were unable 

 to proceed far enough with their researches to enable them 

 to state definitely the yield of acid per kilowatt hour under 

 the best conditions, and on a commercial scale. 



In the April number of the Journal dc Pliysiqne M. A. 

 Dufour gives a detailed account of the examination of 

 the Zeeman effect for certain bands in the emission spectra 

 of gases, on which he has been engaged for the last 

 two years, and of which he has given short accounts in 

 the Comptes rendus. He finds that the bands of the 

 emission spectra of the chlorides and fluorides of- the 

 alkaline earths examined, and of the second or molecular 

 spectrum of hydrogen, may be divided into three classes, 

 the first of which show the normal Zeeman effect in the 

 direction of the magnetic field, i.e. that component of the 

 doublet which has the shorter wave-length is circularly 

 polarised, the direction of rotation agreeing with that of 

 the electric current producing the field. The second class 

 show no appreciable effect, while the third are abnormal, 

 the direction of rotation being reversed, and the polarisa- 

 tion incomplete. M. Dufour is inclined to attribute this 

 abnormal behaviour to negative electrons moving in com- 

 plicated paths determined by the whole of the atoms con- 

 stituting the molecule of the gas, while the normal effect 

 is due 10 the negative electrons moving in comparatively 

 simple paths in the atoms. 



From Messrs. Adam Hilger, Ltd., we have received an 

 eight-page catalogue giving illustrated descriptions, and 

 prices, of several of the spectroscopes specially designed for 

 the observation of stellar and solar spectra. For amateur 

 observers the Zollner star spectroscope, supplied for fifty 

 shillings, is a useful and adaptable instrument. Spectro- 

 scopes for prominence and other solar observations range 

 from 4!. for a small direct-vision, grating instrument, to 

 the 35/. to 60!. " Evershed " protuberance spectroscope, 

 which is a most efficient instrument for the observation 

 of sun-spot spectra and prominences. For laboratory re- 

 searches the Littrow type spectrograph is now largely 

 employed, and a specially designed instrument of this 

 type, having an achromatic objective of 23 inches aperture 

 and 8 feet focal length, and a 2j-inch Rowland or 

 Michelson grating, costs about 65/. 



We have received from Messrs. John J. Griffin and 

 Sons, Ltd., a description of " The York Air Tester," an 

 apparatus for the rapid estimation of carbon dioxide in 

 air. The advantages claimed for this apparatus are that 

 it is simple enough to be placed in unskilled hands and 

 sufficiently accurate for controlling ventilation. It is a 

 niinimetric method, resembling in principle the apparatus 

 described by Lunge and Zeckendorf about fifteen years 

 ago. In the latter apparatus a measured volume of a 

 weak solution of sodium carbonate, coloured with phenol- 



