August 6, 1886.] 



SCIENCE. 



131 



of the wonderful advance of the ' new astronomy ' 

 during the third of a century since Professor 

 Grant wrote, and of the need of a historian for 

 it, can be furnished than the fact that what was 

 then called physical astronomy is now termed 

 theoretical, mathematical, or gravitational ; while 

 to-day by physical astronomy is generally under- 

 stood the investigation of the intimate relations 

 between astronomy, physics, and chemistry as 

 studied in the sun, stars, comets, planets, our own 

 atmosphere, and laboratories. 



Mips Gierke has been peculiarly happy in the 

 rule of historian. Terse and highly original in 

 style, her work will hold the attention of every 

 educated reader for its literary merit alone, while 

 the copious footnote references to the original 

 sources of information ma,ke it a mine of wealth 

 to the student and astronomer. The work is so 

 excellent, and also so rapid is the progress of 

 astronomical discovery, that new editions will 

 rapidly follow ; and for the purpose of making 

 them as valuable and accurate as possible, we 

 trust we shall not be considered hypercritical in 

 calling attention to a few points, either where 

 further comment or criticism would seem desira- 

 ble, or where we think an error of judgment or in- 

 terpretation, or some slight slip of reference or 

 quotation, has been made. Anything but a first- 

 class work we should not consider thus worthy of 

 attention. 



On page viii., for ' Illinois' read ' Madison, Wis- 

 consin.' 



In the closing description of the total disappear- 

 ance of Biela's comet, on pp. 127 and 128, it would 

 seem desirable, for the benefit of the reader igno- 

 rant of the facts, to refer him to the description 

 further on, pp. 377-380, of subsequent encoun- 

 ters with it in the form of meteor showers, the 

 latter now to be supplemented by the shower of 

 last November, since the book was written. 



To the non-astronomical reader, and even to the 

 amateur spectroscopist who only knows of the 

 spectrum as given by an image of the sun cover- 

 ing the whole slit or by some form of integrating 

 spectroscope, the reference on p. 254 to Lockyer's 

 long and short lines will be unintelligible without 

 such a description of his apparatus as will explain 

 that his long or short lines indicated the existence 

 of incandescent shells of vapor at greater or less 

 distances round his electric spark terminals, whose 

 image was thrown on the slit by a lens. 



In the enumeration of phenomena observed 

 during different transits of Mercury, pp, 290 and 

 291 , reference should be made to the one most ex- 

 tensively observed of all, that of 1878, May 5 and 

 6, as described and discussed in the Washington 

 observations for 1876, part ii., app. ii. 



Probably the paragraphs on pp. 304 and 305 re- 

 garding Mr. Croll's theories of secular changes 

 in climate would be somewhat modified since the 

 rather merciless criticism tliese theories have re- 

 ceived at the hands of Woeikof, from the standpoint 

 of a scientific meteorologist. (See Amer. journ. 

 of science for March, 1886.) We can hardly see a 

 justification for the opinion, p. 315, that Professor 

 Langley"s researches lend countenance to the idea 

 that the temperature of the full moon's surface is 

 anything like 500° F. It is difficult to keep up 

 with Professor Langley nowadays, but, so far as 

 we understand his results, they almost certainly 

 point to a temperature below 100° F., and very 

 probably below the freezing point of water. 



Upon reading the letters of Bakhuyzen and 

 Proctor in Nature, xxxiii, pp. 153 and 245. the 

 author will see that the period or rotation of Mars 

 deduced by the former must be incomparably 

 more accurate than Proctor's, and in a new edition 

 Bakhuyzen's later value should be given. 



In spite of the apparent partial confirmation 

 from several sources, we still remain somewhat 

 skeptical regarding Sehiaparelli's canals upon 

 Mars (pp. 324 and 325), especially the duplicate 

 parallel ones. We shall look with interest for the 

 attack upon Mars with the Lick 36-inch refractor 

 when set up on Mt. Hamilton. 



On p. 329, line 3, for 'Vesta " read 'Pallas.' 



As to the idea that the distribution of the aster- 

 oids has been largely influenced by commensura- 

 bility of period with that of Jupiter (p. 329), or 

 that gaps in the rings of Saturn have anything to 

 do with the distances of its satellites, we regard 

 the theory as entirely unproven as yet, and would 

 refer to an article on the subject by Professor 

 Hall in the Sidereal messenger for September, 

 1885, also copied in the October number of the 

 Observatory. 



We question the advisability of referring to a 

 meteor shower as ' star-drift ' (p. 371, line 5), when 

 this term has already crystallized into the definite 

 meaning of community of proper motion among 

 neighboring stars or systems of stars (p. 438). 



The subject of photometry is not adequately 

 treated in the volume. This really deserves a 

 whole chapter, but does not even occur in the in- 

 dex, while the paragraph on p. 435 does no justice 

 whatever to the subject. Several of Professor 

 Pickering's results are incidentally referred to in 

 various parts of the book, but some description of 

 his wonderfully ingenious photometers and meth- 

 ods which have revolutionized the whole subject 

 and given rise to so much discussion is certainly to 

 be expected in a book of this high character. One 

 of the most important of his works, the series of 

 photometric observations of the eclipses of Jupiter's 



