May, miJ 



KNOWLEDGE. 



201 



lights the latter. The Promethian match, which was patented 

 in 1828. contained a tube of sulphuric acid surrounded by a 

 mixture of chlorate of potash and sugar. Walker, of 

 Stockton-on-Tees, however, sold his first box of friction 

 matches on .-^pril 7th. 1827. "Lucifers" were ignited by 

 being drawn through folded sand paper. "" Congreves," 

 again, could be struck upon the box. Mr. Hidwell's 

 catalogue describes a number of other forms which have 

 played their part in the evolution of the match. .,, ,. ... 



ASTKONO.MV. 



Tlic Scuitcc of the Sfiirs.—\iy E. Waltku Maunder. 

 95 pages. 6} -in. X 4.2 -in. 



<T. C. & E. C. Jack. Price 6d. net.) 

 The author is well known to readers of " K.vovvLEDGE," and 

 has compressed a surprising amount of information into the 

 short compass of ninety pages. The early chapters give a short 

 summary of the matter given more fully in the author's other 

 books, " The Astronomy of the Bible " and " .Astronomy with- 

 out a Telescope." There follows a carefully written chapter on 

 "The Law of Gravitation." "Astronomical Measurements." 

 leads us up from the primitive obelisk and dial to the invention 

 of the telescope, and a few of the results of exact astronomy. 

 There is then a physical chapter discussing the telescopic 

 appearance and probable condition of the orbs of the solar 

 system. The final chapter deals with the system of the stars, 

 their distance, number, brightness and motions. It may be 

 safely said that a beginner who has mastered this little book 

 has laid a sound foundation of astronomical knowledge, and 

 is in a better position to tackle larger and more technical 

 treatises. We notice one little slip re Halley"s Comet on 

 page 36. Halley is stated to have identified his comet with 

 those of 1J78 and liOl. Halley in reality erroneously 

 identified it with the comets of 1380 and 1305 ; the correct 

 identifications with those of 1378 and 1301 were made subse- 

 Huentlv bv Langier and Hind respectively. 



'a. C. U. C. 



Tlic .4. /i.e. Guide to Astroiioiny. — By Mrs. H. Periam 

 Hawkins. 120 pages, /i-in. X4i'-in. 



(Simpkin. Marshall, Hamilton, Kent & Co. Price, paper 

 covers. 16 net ; cloth, 2 - net.) 



This is a useful dictionary and glossary of astronomers and 

 their work. The author's name has become familiar to us of 

 late years from her attractive and handy little volumes. 



It is difficult to avoid all inaccuracy in works covering so 

 large a field as this ; a few are noted in the hope that they 

 may be corrected in a future edition, not as implying that the 

 work as a whole is untrustworthy : — 



Page 3. — .Altazimuth : for " reversible transit circle," read. 



" transit circle that can be rotated about a vertical axis. 



so as to point in any direction." 

 Page 6. — M. E. M. .Antoniadi is a Greek not a Frenchniaii. 

 Page 6. — .Aquarids. The showers of May and July are given 



as both connected with Halley's Comet. Only the May 



one is connected with it. 

 Page 14. — Borelli should be Borrelly. He is French not 



Italian. 

 Page 24. — Dr. P. H. Cowell left Greenwich Observatory early 



in 1910. on his appointment as superintendent of The 



Nautical Almanac. Correction also needed page 68. 

 Page 52. — The great eruption of Krakatoa was in 1883; that 



of Mont Pelee (Martinique! in 1902. 

 Page 54. — The use of filar micrometers for .stellar parallax is 



certainly older than the Lick Observatory. 

 Page 66. — It is the eccentricity of the Moon's orbit, far more 



than the evection, that causes the length of the "quarters" 



to differ. Also, their maximum range of difference is only 



one and a half days. 

 Page 67. — Moon's \"ariation. Instead of "The greatest 



impulse in speed is three days before Full Moon," read, 



" The greatest displacement due to the variation occurs 



three and a half days before each of the four quarters." 



Page 76. — Professor Perrine has left Lick Observatory for 



Cordoba. 

 Page 91. — The date of photography of the spectrum of the 



reversing layer should be 1896 not 1876. 

 Page 102. — The Precession of the Equinoxes has nothing to 



do with the Sun's motion in space. 

 Page 108. — The comet of 1862, not Tuttle's Comet, is 



connected with the Perseid meteors. 

 Page 113. — Watson's minor planets were not found by 



photography. 



A. C. D. C. 



.4 PojJular I nlrodnction to Astronomy. — By l\l-.\'. .A. C. 



Hhnuerson. 135 pages. 7 plates. 72-in.X4,'in. 



(T. & J. Manson, Lerwick. Price 2/6 net. I 



This is a chatty and discursive little work, dealing with a 

 few selected (inestions rather than a systematic introduction 

 to the whole science. 



In the chapter on Biela's Comet it is stated that the comet 

 itself collided with the Earth on November 27th, 1872; it 

 would be more accurate to say the swarm of meteors 

 associated with the comet encountered the Earth ; the swarm 

 nuist be much larger than the comet itself. 



We notice some looseness in places in the explanations, thus 

 a Total Eclipse of the Sun is said to take place when the 

 Moon is in Perigee, implying that this is a necessary con- 

 dition ; it is in reality possible in summer for a Total Eclipse 

 to occur when the Moon is at about its mean distance. 



He seems hypercritical in objecting to phrases like "the 

 Sun rises above the horizon " ; they are perfectly legitimate if 

 it be borne in mind that all our ideas of motion are relative. 



Beginners in astronomy will, however, pick up a good deal 

 of miscellaneous information from this book, including some 

 points that are absent from the more conventional handbooks. 



A. c. n. c. 



The Great Star Map.^lW From.ssor H. H. Tirnhr, 



D.Sc.. F.K.S. 159 pages. 1 illustration. 72-in.X5-in. 



(John Murray. Price 2 6 net.) 



There is no one more competent than Professor Turner to 

 write an account of the inception, progress, and partial com- 

 pletion of the Great .Astrographic Star Chart. He took part 

 in several of the conferences that have been held in Paris to 

 settle the details of the work, and both at Greenwich and Oxford 

 he has been most active in pushing on the taking of the plates 

 and their subsecjuent reduction, for which he devised an 

 elegant and simple method, which has been very widely 

 adopted. He commences by tracing the history of photography 

 as applied to astronomy, which now goes back more than half 

 a century, and cjnotes an interesting letter of George Bond's, 

 written in 1857. describing the successful photography of all 

 naked-eye stars, and anticipating that future improvements 

 might extend this to the eleventh magnitude — a daring predic- 

 tion in those days, but now falling far short of the truth. The 

 invention of the dry plate was a great step in advance ; it was 

 far more sensitive than the wet collodion plate, and permitted 

 long exposures, whereas the latter ceased to be sensitive 

 when dry. The number of stars shown on photographs of 

 the great comet of 1882 came as a revelation of the possibilities 

 of the new method, a hint which was quickly taken advantage 

 of by Sir David Gill, Dr. Common, the brothers Henry and 

 others. Finally, a great conference was held at Paris, under 

 the leadership of .Admiral Mouchez. There were advocates 

 of three different forms of telescopes, reflectors, refractors 

 and doublets. The reasons for the choice of the middle form 

 are given ; the whole sky was divided among eighteen observa- 

 tories, all using refractors thirteen and a-balf inches in 

 aperture, with eleven and a-quarter feet focus (l' = lmm.) 

 Another interesting point touched on is the " reseau " of small 

 squares on the plates, originally introduced to detect unequal 

 shrinkage of the film, but retained as a great aid to measurement. 



Star counting on the plates is next discussed, and the fact 

 that the ratio of increase of number of stars per magnitude 

 falls short of its theoretical value four. He inchnes in the 

 book to two explanations : (il a solar cluster of our neighbours 



