December, 1906.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



6ig 



experiments and for diajframs of the apparatus to be drawn 

 to scale. It is intended to supplement, but not to replace 

 the demonstration of the teacher, and we can cordially 

 recommend it as admirably adapted for this purpose. 



MATHEMATICS. 



Five Figure Matliematical Tables, for School and 

 Laboratory Purposes, by A. Du Pre Denning, M.Sc, etc. 

 (London : Lonijmans, Green and Co., 1906; price 2s.).— This 

 set of tables possesses several oriejinal features. The author 

 notices that the mean differences become unwieldy in tables 

 of logarithms of small numbers {i.e., numbers near unity), 

 and also in tables of antilogarithms of large numbers. His 

 way out of the difficulty is to give antilogarithm tables for 

 numbers up to 4 or logarithms up to .61, and logarithm 

 tables for numbers above 4. The plan certainly saves two 

 pages, which would be required if antilogarithms and 

 logarithms of all numbers were given, and these two pages 

 are devoted to antilogarithms and logarithms of reciprocals 

 arranged similarly. The trigonometrical tables are not as 

 clearly ari'angcd as they might be, and we notice with regret 

 that the " tabular " logarithms are denoted by Log, in- 

 stead of by the old conventional L. !f reforms of notation 

 are desirable, let reformers turn their attention to the mis- 

 leading forms, sin-', cos-', and tan-^, before they do away 

 with such a non-misleading symbol as a capital L. The 

 book contains physical and chemical tables, and those 

 students who want to solve triangles without properlv learn- 

 ing their trigonometry will llnd the tables of squares and 

 cubes greatly to their liking. 



METEOROLGY. 



Falmouth Observatory Meteorological and Magnetical Tables 

 and Reports for the year 1905. — This Observatory is 

 maintained by the Royal Cornwall Polytechnic Society, and 

 is under the supervision of a committee of which Mr. Wilson 

 Lloyd Fo.x is secretary. Mr. Edward Kitto is the superin- 

 tendent of the Observatory. The Meteor )logical Office 

 allows an annual grant of .£^250 for the carrying on of the 

 meteorological records, and the Royal Society makes a 

 grant of ;^"'53 and the British Association a grant of £50 

 towards the maintenance of the magnetic records. The 

 present report not only gives the results of the meteorologi- 

 cal observations for the year 1905, but also the averages for 

 the 35 years, 1 87 1- 1905. The averages of the principal 

 elements are as follows : — 



Tenipcr.iture. Riiiiifall. Sunshine. 



Nn.of No. of 



Oailv K;miiv H.inless 



Mcnlhs. Mem. K.iiiBe. Anioum. Days'. Amount Days. 



January ... 45.4 6.S 4.76 20 57.1 12 



February ... 43. j 6.g 3.76 17 82.8 7 



March ... 43. S 8.4 3.31 iS 137-7 5 



April ... 47.4 9.1 2.84 15 180.2 3 



May ... 51.8 10.4 2.21 13 236.4 2 



June ... 57.3 10. tj 2.42 14 22S.8 2 



July ... 60.2 10.6 3.12 16 226.1 I 



August ... 59.9 lo.o 3.48 16 213.9 I 



.September ... 56.8 8.g 3.69 17 160.2 ^ 



October ... 51.3 8.1 5.15 20 116. 6 =, 



November ... 47.4 7.2 5.27 19 73. 8 8 



December ... 44.6 6.6 5.74 21 55.4 12 



Year ... 50.6 8.6 45.75 206 1769.0 61 



The mean magnetic declination for the year 1905 was 



18" 8'.4 W. Falmouth Observatory is in latitude 



50° 9' o'/ N, and longitude ^'^ 4' 35'' \V. 



NATURE STUDY. 



We have n-ceived a copy of " Blackie's Nalure-KnowU-dge 

 Diary," compiled, with introductorv notes on nature-studv, 

 by Mr. W. P. Westell, and sold at"6d. net. Careful record 

 of all observations, no matter how trivial they may appear, 

 is the point specially emphasised in the notes. The pub- 

 lishers, Messrs. Blackie and Son , Limited, olTer prizes 

 to school-children for the best-filled copies of the diary. 



PHOTOGRAPHY. 



Photographic Lenses ; A Simple Treatise, by Conrad 



Heck .iiul Herbert .\iuli(\v>. (ilh ciiition, revised (London: 

 R. and J. Beck, Ltd., and Percy Lund, Humphries and 



Co., Ltd.; price is. net.). — The fact that fifteen thousand 

 copies of this book have been called for shows that it has 

 met with practical appreciation, and we think that it well 

 merits the patronage it is receiving. The title is perhaps 

 rather too broad, for one might imagine from the constant 

 and exclusive references to lenses made by Messrs. R. and 

 J. Beck, that this firm were the only makers of photographic 

 lenses. But as Messrs. Beck make lenses of most of the 

 ordinary types, including the most modern, the reference to 

 their own instruments only does not notablv limit the scope 

 of the volume. The authors aim at providing a practical 

 guide for practical photographers who do not wish to dip 

 deeply into the subject of photographic optics. No one of 

 ordinary intelligence can read the volume without getting 

 a very good idea as to what lenses are, how they should be 

 used, and what may generally be expected of them. The 

 numerous illustrations show at a glance the elTects described, 

 and the kind of result that may be obtained under certain 

 conditions. We are glad to see that spherical aberration is 

 given as one of the elements that affects depth of definition, 

 but we think that the authors might have departed from the 

 too common custom of considering depth of definition in the 

 centre of the field only. This is not a " practical " method 

 of dealing with the subject. .Another suggestion may per- 

 haps be made, that, with regard to curvature of field, the 

 character of the object might be defined, for it is not often 

 enough realized that the image produced is generallv, as 

 it were, a solid image, neither curved nor flat, and bears 

 110 very simple relationship to what is properly called the 

 field of the lens. 



MISCELLANEOUS. 

 Natural Phenonema ; A Collection of Descriptive acd 

 Speculative Essays on Some of the By-Paths of Nature, 

 by F. .\. Black (Gall and Inglis).— This collection of ideas 

 on some of the mysteries still unfathomed by man, includes 

 chapters dealing with the variations of temperature, the 

 peculiarities of the North Pole, the apparent enlargement 

 of heavenly bodies near the horizon, weather cycles, the 

 Sargasso Sea, the Zodiacal light, wind, varieties' of Solar 

 days, the rotation of the earth, and the diurnal variations 

 of the barometer. Each of these subjects is clearly de- 

 scribed, and its uncertainties discussed, while a number of 

 diagr.ims, maps, and illustrations add to the lucidity of the 

 descriptions. The frontispiece, a fanciful representation 

 of the Zodiacal light, is the weakest feature of the book. 



The Science of Dry Fly-Fishing, by F. G. Shaw (London: 

 Bradbury, .\gnew, and Co., Ltd., 1906; pp. xii. + 142; price 

 jS. 6d. ret). — The observant angler has such abundant 

 means of studying n.itural history, either as an essential 

 part of his sport, or for its own sake, that we are quite glad 

 to have the opportunity of noticing the work before^ us 

 among books of a more strictly scientific nature. The 

 author, whose name has previously been before the publl-: 

 on more than one occasion as a writer, appears to be a 

 most accomplished fisherman, having gained the amateur 

 championship in a recent fly-casting tournament. 

 Whatever he states on the subject mav, therefore, v.o 

 presume, be accepted as thoroughly trustworthv, so that the 

 book may be confidently recommended to lovers' of the gentle 

 art. .An .Utiactive coloured plate of a basket of trout from 

 the Itcheii forms the frontispiece to this exhaustive work. 



-Messrs. Henry Sotheran' & Co. arc publishing, under the 

 title of " Bibliotheca Chemico-Mathcmatica," a valuable 

 catalogue of works, chiefly rare or historical, on mathe- 

 matics and astronomy, physics, aeronautics, chcmistrv, and 

 other scientific subjects. The catalogue is being issued in 

 parts, and in its complete form should be of great use to 

 librarians or scientific men who wish to complete or fill up 

 libraries, .\mong other works of special interest, we note 

 the extremely rare first edition of the " De Revolutionibus," 

 of Copernicus, which itself marked a " revolution " in 

 thought; the first printed edition of "Euclid"; the first 

 work on " Ballooning " (Faujas de St. Fond " Experiences 

 de la Machine Aerostatique de MM. de Montgolfier ") ; and 

 the first edition of " De Caux's " Raisons des F"orces 

 Mouvantes," which, according to .\rago, contained the germ 

 of the Steam Engine. 



