January ii, 191 2] 



NATURE 



)45 



Evans's volume, would be very much astonished to be 

 told that probably no single atomic weight is known 

 to o"oi per cent., and that comparatively few are 

 certain to one part in a thousand. Indeed, it may 

 almost be asserted that there is just as much a pre- 

 vailing "fashion" in atomic weights as in that of 

 wearing apparel. In view of the fact that laboratory 

 chemistry may be said to have had a start of nearly 

 a century upon laboratory physics, this great dis- 

 crepancy in the precision attainable in the two sciences 

 is not easy to explain, the difference being the more 

 remarkable when the relative numbers of workers in 

 the two fields are taken into account. 



Possibly after all the theorising to the contrary the 

 true cause may be found to be that all the atoms of 

 a so-called elementary substance have not exactly the 

 same weight. J. A. Marker. 



PRACTICAL ASTRONOMY. 



Text-book on Practical Astronomy. By Prof. G. L. 

 Hosmer. Pp. ix + 205. (New York: John Wiley 

 and Sons ; London : Chapman and Hall, Ltd. ; 

 iqio.) Price 85. 6d. net. 



THOSE who have used Prof. Hosmer's previous 

 work, "Azimuth," will remember that one of 

 its most pleasing features is the unconscious display 

 of the author's intimate acquaintance with the prac- 

 l side of surveying and of teaching. The same 

 I : -iing feature is just as much a characteristic of 

 ilv present work. One feels that there is but little 

 lie subject that the author has not practised until 

 operations are almost part of a second nature, 

 in this work he does not lose sight of the fact 

 the student is a beginner and needs telling that 

 sun-glass is not usually placed over the object- 



The order of treatment is the conventional one; 



till' method of treating the subject is Prof. Hosmer's. 



he early chapters he explains, with numerous 



>Ie diagrams, the real and apparent motions of 



celestial sphere, gives a number of definitions, 



III then describes the common systems of coordinates, 



th' ir interrelations, and the methods of converting 



qii.intities from one to the other. 



I lie anomalies of our unscientific mixture of 

 lies " are elucidated in the next chapter, and the 

 iint is shown by example how to obtain any one, 

 knowing either of the others. In chapter vi. the 

 American ephemeris is explained, but much of the 

 matter would apply equally to the contents of our 

 Nautical Almanac ; the method of interpolation to get 

 intermediate ephemeris values is simple, but Prof. 

 Hosmer recognises that it is not so simple — to the 

 student — as to need no explanation. After consider- 

 ing the figure of the earth and the corrections it 

 renders necessary, the author proceeds to a chapter 

 on instruments, where, after dealing with the 

 engineer's transit, the sextant and the chrono- 

 r, he gives a brief and simple account of the 

 li telescope and concludes with a characteristic 

 L^^raph (58) of hints and suggestions on observ- 

 the hint as to the mnUing of a permanent mark 

 ' ing the focus nn ,1 frequently used surveyor's 

 NO. 2202, VOL. 88] 



transit telescope illustrates how simple the author has 

 made it for a beginner to " go right." 



In the subsequent main chapters on the determina- 

 tion of latitude, time, longitude, and azimuth, we do 

 not detect any novel methods, but we do recognise 

 the simple conciseness of the instructions. By the 

 use of smaller print the matter for a longer (advanced) 

 course is differentiated from the simpler matter which 

 would form a good first, or short, course — a hint that 

 is valuable from such an experienced instructor. The 

 formulae employed are all numbered, so that in the 

 case of transformations, or derivations, the student 

 can readily refer back to his primary form. 



The concluding chapter, on nautical astronomy, is 

 chiefly notable for its excellently clear statement of 

 Sumner's method illustrated by one or two useful 

 diagrams. In an appendix the general question of 

 tides is discussed briefly from the point of view of 

 "level," and a number of useful tables of various 

 astronomical quantities are given. The diagrams 

 throughout are numerous, clear, and readily com- 

 prehensible. 



THE MENACE OF THE HOUSE-FLY. 

 The House-fly — Disease Carrier: an Acr.nint of Us 

 Dangerous Activities and of the Means of Destroy- 

 ing it. By Dr. L. O. Howard. Pp. xix+312. 

 (New York : Frederick A. Stokes Co., 191 1.) Price 

 1.60 dollars net. 



ALTHOUGH house-flies are universally admitted 

 to be a nuisance of a peculiarly exasperating 

 kind, it was not until almost within the last decade 

 that even physicians, with a few isolated exceptions, 

 began to realise the possible dangers lurking in the 

 presence of the most familiar and probably rnost 

 widely distributed of all insects. The Spanish- 

 American war of thirteen odd years ago did something 

 to direct attention to the importance of the house-fly 

 as a carrier of enteric fever in military standing 

 camps, and the lesson then borne in upon the medical 

 oflicers of the United States Army was enforced only too 

 well a few vears later by our own experiences in South 

 Africa. It is now agreed by those best qualified to 

 judge that the house-fly can convey the causative 

 agents of cholera and enteric fever, and in outbreaks 

 of these diseases often plays no inconsiderable part as 

 a disseminator. Whether or not it acts as a carrier 

 of infantile diarrhoea, which during the summer 

 months frequently causes great mortality among 

 young children, is not yet conclusively established; but 

 that it is capable of carrying tubercle bacilli is certain, 

 and tuberculosis and the other diseases mentioned do 

 not exhaust the list of what are at least potential 

 dangers connected with the house-fly. 



In the so-called "residential" quarters of cities, in 

 countries such as our own, the house-fly has now- 

 adays not much opportunity of becoming contaminated 

 with disease-causing organisms, but. as has been 

 shown by Prof. Newstead in Liverpool, and in Wash- 

 ington hv the author of the volume before us, it is 

 unfurinn.i i. K- otherwise in the dwellings of llir poor. 

 Ill \ill.Li;i-.s iind old-fashioned farmhouses, where sani- 

 t,,i\ iirangements are too often painfully primitive, 



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