518 



SCIENCE 



[N. S. Vol. XXXVIII. No. 980 



considerations of economy it put a stop to the 

 practise formerly permitted of computing ap- 

 parent places. When, from the same cause, 

 the American Ephemeris found room between 

 its covers for tables of Polaris facilitating 

 azimuth determinations, the survey was quick 

 to take advantage also of these tables (p. 17). 



With regard to Mr. Duvall's ingenious de- 

 vice for the graphical determination of the 

 A, B, C factors of Mayer's formula, it may 

 be stated that this is not the first time such a 

 device has been put forward. Plate XII., 

 Astronomical Observations of the U. S. Naval 

 Observatory, Washington, 1846, with descrip- 

 tion on pp. xliv et seq., illustrates a similar 

 solution of the same problem by Bessel's for- 

 mula, the chart being adapted to the deter- 

 mination of m + n tan 8, and also, with the 

 aid of an auxiliary table, of c sec 8. 



The difficulty encountered in the footnote 

 on p. 270 of the former edition has been neatly 

 surmounted in the new. 



Another novel feature is the inclusion of a 

 treatise on time determinations with the ver- 

 tical circle. It would not be surprising to find 

 the next edition include also an account of the 

 astrolabe. Eecently developed by the French, 

 and claimed by them to give results com- 

 parable with those obtained by the portable 

 transit, this instrument has much to commend 

 it. It is as portable as a theodolite, requires 

 no firm-set pier, is easily manipulated, and the 

 same observations employed for time may be 

 used also for latitude.' On the other hand, 

 the computations, both preliminary to and fol- 

 lowing the observations, are heavy; and the 

 most serious obstacle encountered with this 

 instrument, if all accounts are to be believed, 

 would seem to be that old and familiar stum- 

 bling-block, personal equation. 



Prom a literary standpoint the new edition 

 is markedly improved. Where in the older 

 volume the diction was awkward, it has here 

 been replaced by wording more smooth and 

 elegant. Here and there a sentence has been 

 altered for clearness, or a phrase added to 



- See Chauvenet 's ' ' Spherical Astronomy, ' ' Vol. 

 I., p. 280, and Claude et Drieneourt's "L 'Astro- 

 labe fl Prisma." 



supply an idea previously left to the fruitful 

 imagination of the reader. Where a para- 

 graph or a sentence was superfluous, it has 

 here been omitted. The numbering of the 

 sections has been done away with, and more 

 headings have been supplied for sections which 

 properly should appear as such. It can not he 

 said, on the other hand, that the change from 

 words to figures when referring to numerals is 

 a decided literary advantage; nor that all 

 omissions have been improvements. On p. 23, 

 for example, there might have been retained 

 in its proper place the remark on p. 281 of the 

 former edition, " Por a discussion of this mat- 

 ter, see — ." Among minor changes may be 

 noted slight modifications of notation to pre- 

 vent confusion, and the substitution of nu- 

 merals for asterisks and daggers. The con- 

 tinuity is broken by continual switching from 

 discussion of methods with the transit mi- 

 crometer to those with the key, but to offset 

 this the book is of increased value as a more 

 complete manual. 



Of the various methods for determining 

 longitude, the ordinary telegraphic and the 

 chronometric are treated fully. Lunar and 

 other methods less frequently employed in the 

 survey are merely mentioned on p. 78. Deter- 

 minations by wireless telegraphy, though al- 

 ready employed in Europe and by the Ameri- 

 can Navy are still in the experimental stage. 

 This will without doubt be the method of 

 the future, and the proposed determination 

 of the difference of longitude between the 

 U. S. Naval Observatory and the Observatory 

 of Paris, as well as a similar trans-Atlantic 

 scheme under contemplation by the survey 

 authorities for the near future, should aid 

 greatly in the development of this method. 



The publication is highly creditable to the 

 officers of the Coast and Geodetic Survey, and 

 the reviser and part author is to be con- 

 gratulated upon maintaining so well the high 

 standard set by his predecessors, Schott and 

 Hayford. 



David Eines 



The Climate and Weather of San Diego, Cali- 

 fornia. By PoRD A. Cabpenter, LL.D,, 



