328 



NA TURE 



[February 2, 1905 



Andrade, based on his own experiences in the University 

 of Besan^on, and finally, M. Louis Couturat, of Paris, 

 contributes a paper on " The Definitions of Mathematics." 



A SERIES of articles by Mr. E. Edser on the " Electro- 

 magnetic Theory " is appearing month by month in 

 Technics, and should prove useful to students of physics. 

 The article contributed to the January issue deals with the 

 electric circuit. A very simple method is given of deter- 

 mining the force on a conductor carrying an electric cur- 

 rent perpendicular to a magnetic field, and this result is 

 used to obtain an expression for the electromotive force 

 produced when a conductor cuts lines of force. The re- 

 sults, of course, are well known, and are used by every 

 electrical engineer, but the reasoning by which they are 

 obtained is not so widely understood. Most of the results 

 are determined directly from the properties of lines of 

 force, and the usefulness of the article is greatly increased 

 by careful scale drawings. 



Messrs. R. and J. Beck, Ltd., supply, for one guinea, 

 a glass trough, 4x3x0.8 inches, which can be raised or 

 depressed on a vertical metal upright a distance of from 

 ij inches to 10 inches from the table. This trough forms 

 a simple form of light filter when filled with liquid, and 

 will serve not only as a- useful adjunct to a microscope, but 

 for many other purposes where it is of advantage to use a 

 screen for monochromatic light. 



Messrs. Taylor, Taylor and Hobson, Ltd., have 

 recently issued two series of rapid Cooke lenses that 

 should prove of great service, not only in high-speed photo- 

 graphy, but for the finest portraiture and for difficult 

 subjects under fair conditions of lighting. They are 

 known as the Series iv. and ii., and have full apertures 

 of f/s-d and //4.5 respectively. The makers have fully 

 developed in these new lenses the advantages of construc- 

 tion of their well-known Series iii. and v. Cooke lenses. 

 The leaflet, which contains details and prices of these 

 lenses, includes some striking illustrations of the work 

 accomplished by them. 



We have received from Messrs. Burroughs Wellcome 

 and Co. their photographic exposure record and diary, 

 which is a most handy pocket book and contains many 

 new features. The monthly light tables are now placed at 

 the end of the book, and the order of the months has been 

 reversed so that the current month faces the exposure 

 calculator, each month being torn off as it passes. This 

 renders the calculation of an exposure a very simple pro- 

 cess indeed. There is also ample room for recording 

 details of plates exposed, facts relating to positive ex- 

 posures, and ordinary notes and memoranda, for each of 

 which three separate sets of pages are available. In 

 addition to these and other items of useful information 

 for photographers, there is a serviceable article on exposure, 

 giving complete instructions for using the calculator pro- 

 vided, a'concise explanation of the factors governing correct 

 exposure, and an up to date list of the speeds of all plates 

 and films, including, besides British, a number of .American 

 and Continental brands. Bound in a neat cover, with 

 pocket and pencil attached, this excellent, cheap, and 

 compact little pocket encyclopa;dia of photography should 

 be in great demand by all workers, whether amateur or 

 professional. 



Mr. W. B. Clive has published new and enlarged 

 editions of parts i. and ii. of Dr. G. H. Bailey's " Tutorial 

 Chemistry." Both volumes have been edited by Dr. 

 William Briggs. 



NO. 1840, VOL. 71] 



The Engineering Standards Committee has now issued 

 its report on pipe flanges. It is entitled " British 

 Standard Tables of Pipe Flanges," and is published by 

 Messrs. Crosby Lockwood and Son at 2s. 6d. net. 



The Department of Revenue and Agriculture of the 

 Government of India has published the agricultural 

 statistics of India for the years 1898-9 to 1902-3, in two 

 volumes. The first part is concerned with British India 

 and the second with the native States. The voluminous 

 particulars have been compiled under the supervision of 

 the director-general of statistics. 



Several catalogues of physical, chemical, and other 

 scientific apparatus have been received from Messrs. Brady 

 and Martin, Ltd., of Newcastle-upon-Tyne. Among in- 

 teresting instruments described in a supplement that brings 

 a larger catalogue up to date may be mentioned Sodeau's 

 new form of gas analysis apparatus, and Seger's cones for 

 the determination of the temperature of furnaces, kilns, 

 &c. A special supplementary list of new apparatus for 

 experiments in physics includes particulars of simple ap- 

 pliances described in recent text-books of practical physics 

 which are largely used in the laboratories of schools and 

 colleges. 



The story of the Zeiss works at Jena is of deep interest, 

 both in its scientific and sociological aspects. Prof. F. 

 Auerbach described the Jena enterprise in a volume pub- 

 lished in 1903. This work has now been translated into 

 English by Mr. S. F. Paul and Mr. F. J. Cheshire, and 

 published by Messrs. Marshall, Brookes and Chalkley, Ltd., 

 under the title " The Zeiss Works and the Carl-Zeiss 

 Stiftung in Jena." A short account of the creation and 

 progress of these great cooperative works was given in 

 the obituary notice of Prof. Ernst Abbe which appeared 

 in last week's Nature (p. 301). Many other interesting 

 particulars will be found in the English edition of Prof. 

 .\uerbach's book, which is a popular description of the 

 development and importance of a concern that offers 

 valuable lessons to students of physics, technology, and 

 social science. 



OUR ASTRONOMICAL COLUMN. 



Astronomical Occurrences in February: — 

 Feb. 5. gh. 7m. Minimum of Algol (/3 Persei). 



8. 2h. Conjunction of the Moon and Venus. Venus 



3° 20' N. 

 ,, 5h. 56m. Minimum of Algol (5 Persei). 



9. iSh. Conjunction of the Moon and Jupiter. Jupiter 



2° 49'. 



13. 5h. 12m. to 6h. 32m. Moon occults 6- Tauri 



(mag. 3-6). 

 „ 5h. 14m. to 6h. 29m. Moon occults 6' Tauri 

 (mag. 3-9). 



14. I2h. Venus at greatest elongation, 46° 41' E 



,, Venus. Illuminated portion of disc = o 516, of Mars 

 = 0903. 



18. 5h. 53m. to 8h. 9m. Transit of Jupiter's Satellite 



III. (Ganymede). 



19. Partial eclipse of the Moon, partly visible at 



Greenwich. 

 ,, 4h. 41m. First contact with penumbra. 

 ,, 5h. 34m. ,, ,, shadow. 



,, 7h. cm. Middle of the eclipse. 

 ,, 8h. 7m. Last contact with shadow. 

 „ 9h. 19m. ,, ,, penumbra. 



Moon rises at Greenwich at 5h. i6m. 



Magnitude of the eclipse = 0"4lo. 

 21. loh. 5m. to loh. 40m. Moon occults -q Virginis 



(mag. 40). 

 24. Vesta 3' N. of 8 Virginis. 

 28. 7h. 40m. Minimum of Algnl (/3 Persei). 



