August 3, 1882] 



NX TURi 



3 J 9 



eluding those of Crompton, Biirgin, Jaspar, and Serrin. 

 Lamps adapted for use in series or derivation, including 

 the so-called differential lamps, are considered in a sepa- 

 rate chapter. Amongst the forms described arc those of 

 Gramme, Weston, Brush, Hefner-Alteneck (Siemens), 

 Gulcher, and the Pilsen lamp. According to the author, 

 the differential lamp of von Hefner-Alteneck was the first 

 to make practical the introduction into one circuit of a 

 number of lights. Jablochkoff's well-known candle, and 

 its more recent imitations are described briefly, and then 

 the author passes to the semi-incandescent lamps of the 

 Werdermann type. Edison's incandescent lamp is next 

 described, as it was in the year 1S79. All Edison's more 

 recent improvements appear to be unknown to the author, 

 who passes by the Edison exhibit at the Paris Exposition 

 with a compliment upon the good quality of its colour ! 

 The incandescent lamps of Lane-Fox and of Maxim are 

 both described and figured, whilst that of Swan— ante- 

 cedent to both of the latter, as well as to Edison's carbo- 

 nised filament lamp — is described only, and not figured. 

 Details concerning driving-power, distribution, cost, and 

 fire-risks follow. Applications of dynamo-electric ma- 

 chines to metallurgy, electro-chemistry and telegraphy, 

 make a chapter in themselves, as also does the subject of 

 the electric transmission of power. A penultimate sec- 

 tion deals with storage batteries, in which we are glad to 

 observe that full justice is done to Plante", the inventor of 

 the accumulator. A rather sketchy chapter on the mathe- 

 matical theory of electric arc lighting closes the work. 



On the whole, though this work contains useful infor- 

 mation on many points, it is much to be regretted that it 

 is not so complete as might have been hoped of a book 

 published in 1882. In a science whose applications are 

 developing so fast, this incompleteness detracts greatly 

 from the value of the work. 



OUR BOOK SHELF 



The Watchmaker's Handbook. By Claudius Saunier. 

 English Edition, Translated, Revised, and considerably 

 augmented by Julian Tripplin and Edward Rigg, 

 M.A. 



There is no trade, we suppose, in which so many special 

 tools are used as in watchmaking, nor any in which the 

 character of a workman is so readily distinguished by 

 them. The good workman has good tools — a perfect 

 army of them — nearly all self-made, with which he is 

 prepared to execute any piece of work, in a neat, clean, 

 and efficient manner. 



This little book describes watchmakers' tools, but 

 deals with many operations inadmissible from a manufac- 

 turer's point of view. " Every watchmaker," says the 

 preface, " will at once recognise that receipts are included 

 which are of the nature of makeshifts, and that it would 

 in many cases be better to replace a piece by a new one, 

 rather than to repair it it in the manner indicated." But 

 there is good reason for this : — "The immense number of 

 badly-constructed watches that he (/he workman)is called 

 upon to put in going order for a trifling remuneration, 

 compels him to replace the older methods of procedure 

 by others, whenever by so doing time can be saved.'' 



If watches were as big as steam-engines there are few 

 people who would not be horrified at the kind of work 

 put into some of them. But they go well ? so they may 

 (or may not), thanks to a strong mainspring, until they 

 are pulled to pieces. 



All watch repairers, or "jobbers," as they are techni- 



cally called, and manufacturers too, ought, however, to 

 be interested in this book. It contains a great deal of 

 useful and instructive information, and it must be left to 

 the consciences of such as to the suggestions herein con- 

 tained, they would, or would not, adopt. 



H. Dent Gardner 



Deseriptiones Plantarum Novarum et minus Cognitaiutn. 



Fasc. viii. Auctore Dr. Regel. Pp. 150. (St. Peters- 

 burg, 1 88 1.) 

 The Director of the Imperial Botanic Garden describes 

 a number of novelties cultivated under his own eye. One 

 of the most striking is a new Crinum, (C. Schmidti) from 

 Port Natal, which scarcely seems separable by descrip- 

 tion from C, latifolium, L. The bulk of the pages, how- 

 ever, is filled with an enumeration of the glumaceous 

 plants at present known from Central Asia, in the study 

 of which Aitchison's Afghan collections have not been 

 overlooked. 195 species of Gramineae are enumerated, of 

 which 79 are Asiatic, or at any rate are not known from 

 Europe ; 75 species are middle European or Mediter- 

 ranean ; and 37 arc common to middle Europe, middle 

 Asia, and North America. 



Turning over Dr. Rcgel's pages affords a ready illus- 

 tration of the wide diffusion of the components of the 

 British flora. Without pretending to absolute accuracy, 

 we noted that of the 109 species of the British grami- 

 neous flora, 65 are recorded by Dr. Regel from Central 

 Asia. We looked with some curiosity to see if any light 

 was thrown on the origin of our cereals. But though rye 

 ySeeale cereale) appears to occur in a wild state in Turk- 

 estan, the forms of wheat met with by botanical collectors 

 were all represented by cultivated specimens. Dr. Regel 

 does not seem to have met with, from Central Asia, 

 Wingerkuthia Africana, obtained by Aitchison in his 

 second journey ; although only known to botanists from 

 South Africa, it was found to be one of the chief fodder- 

 grasses ol the Lower Kuram Valley. 



LETTERS TO THE EDITOR 



[The Editor dots not hold himself 'responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is taken of anonymous communications. 



[ The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible otherwise to ensure the appearance even 

 of communications containing interesting and novel facts.] 



The Spectrum of the Light emitted by the 

 Glow-worm 



I AM not aware that any account has been published of the 

 nature of the light emitted by the glow-worm, and therefore 

 venture to send the results of some observations I made on the 

 evenings of the 21st and 22nd of the month. 



The light, as is well known, proceeds from the lower urface 

 of the penultimate and ante-penultimate segments of the lower 

 abdomen of the insect, and also from two round sp it 

 last segment — it is of a greenish colour, and when 1 

 n ith the spectroscope gives a short continuous spectrum extending 

 i Cto*, and therefore containing ray; of all wave- 

 lengths between 656 and 51S— the more refrangible p 

 far the brightest, and the general appearance is of a broad band 

 of green light reaching from about 5S7 to 518, with a faint con- 

 tinuous spectrum extending down into the red. 



I may add that the observations were made with a small 

 direct-vision spectroscope, with a photographic scale ; and also 

 that glow-worms are extremely rare in this district. 



Reading, July 29 John Conroy 



Oscillations of the Sea-level 



It seems to be very generally assumed that the surface of the 

 ocean attains a uniform level, or nearly so, in all lands, and 

 forms a sort of zero-point or datum line, from which the altitude 



