oo4 



- KNOWLEDGE ♦ 



[Nov. 30, 1883. 



simpler language, the combination of the nascent hydrogen 

 with oxygen of the bichromate of potash, proceeds less 

 rapidly than might be desired. The result is that the con- 

 stancy of the cell is materially impaired. To overcome 

 this difficulty several devices have been brought forward. 

 Amongst them is the pneumatic cell, in which air is 

 forced into the cell at the bottom of the plates, and, rising 

 through the solution, carries off the hydrogen as it collects on 

 the carbon plates. This arrangement also serves to keep 

 the solution in motion, constantly supplying fresh salt to 

 the plates. The cell cannot, however, be regarded as a 

 very practical one, and we shall soon consider others 

 which achieve a similar object in a less troublesome 

 manner. 



PONS' COMET. 



THE comet (Pons-Brooks) was observed by me in 

 Liverpool, November 17, between 6 h. 15 m. and 

 7 h. p.m. ; the right ascension being 17 h. 4-t m. declination 



i^rbitUisi* 



EVOLUTION AND NATURAL THEOLOGY.* 

 By Edward Clodd. 



THIS is a book of much interest from the pen of a 

 ready writer. Mr. Kirby has already scored honours 

 in the scientitic world as an expert in entomology, and his 

 experience in classitication serves him in good stead in the 

 arrangement of the mass of material, which, in a volume 

 of about 200 pages, can be treated only in a summary 

 fashion. Whilst, however, neglecting no important feature 

 of the theory which lie expounds, Mr. Kirby has shown 

 literary skill in preventing his little book from becoming a 

 mere catalogue. As will be seen presently, the spact- 

 given to matters which are no essential part of the theory 

 of evolution is to be regretted, because it might have been 

 devoted witli advantage to more detailed reasoning in 

 support of that theory. From the like cause, the argu- 



north 49° 36'. It has greatly increased in brilliancy since 

 October 3, shining as a star of the 7th magnitude ; with a 

 magnifying power of 30, a stellar point could be discerned, 

 situated eccentrically within the elongated disc. It may 

 be found with a field glass, and is a comparatively easy 

 object in a telescope of two icc'ies aperture. The peri- 

 helion passage takes place on Jan. 14, 1884 (in right 

 ascension 23 h. 12 m, declination south 1° 10'), at a dis- 

 tance of .33 ' from the sun. This comet, whose identity 

 ■with that of 1812 has now been proved, was discovered by 

 Pons, of Marseillps, on July 20, 1*^12, in the constellation 

 Lynx. It shortly afterwards developed a tail 2° long, and 

 •was visible to the naked eye for ten weeks. The portion 

 of the heavens represented in the map is taken from 

 Proctor's " Star Atlas " ; the path of the comet from 

 November 13 to December 29 is projected from Chandler's 

 corrected elements of Schulhoff and Bossert. On Jan. 30, 

 1884, it will be in Cetus, on February 13 in Sculptor, and 

 after the latter date will be invisible in these latitudes, 

 owing to its great southerly declination. 



W. K. Bradoate. 



ments in its favour furnished by philology and by the 

 important transitional forms of organisms, are tantalisingly 

 meagre, whilst the discussion upon Sir William Thomson's 

 bizarre theory of the origin of life — namely, that if a 

 mass of matter from an inhabited world fell upon an un- 

 inhabited world, the adhering germs would in time stock 

 that world with life — could have been well spared. The 

 work opens with a well-condensed sketch of ancient specu- 

 lation concerning the earth and its place in the universe 

 as contrasted with modern theories founded on observation 

 and experimont, and in succeeding chapters the steps by 

 which scientists of the eighteenth and nineteenth centuries 

 have been led to substitute for the old theories of special 

 creation and the fixity of species theories more tenable, 

 which have finally culminated in the brilliant generalisa- 

 tions of Mr. Spencer and Mr. Darwin, are clearly laid 

 down. Mr. Darwin's explanation of organic evolution is 

 then passed in review, and the general body of evidence 

 upon which it is based suaimarised, with the needful quali- 



* " Evolation ami Natural Theology." By W. F. Kirby, of tho 

 British Museum. (W. Swann, Sonneschein, & Co. 1883.) 



