388 



SCIENCE. 



[Vol. V., No. 118. 



is only apparent in high velocities. For nearly 

 all studies, it will suffice to consider the deflec- 

 tions as if produced on a sphere. 



Ritter's speculations concerning the gaseous 

 condition of the earth's interior are of espe- 

 cial importance, inasmuch as they may tend to 

 counteract the very positive statements made 

 by English physicists and geologists in recent 

 years in regard to the age and contraction of 

 the earth as determined by its cooling. The 

 English school generally regards the earth as 

 essentially solid, with a great central volume 

 of dense matter at a high, and, roughly speak- 

 ing, uniform temperature. On the basis of 

 certain plausible assumptions concerning the 

 original temperature and conductive power of 

 the mass, it has been possible to approximate 

 fairly well to the age for an earth of such char- 

 acters, and to determine roughly the shortening 

 of its radius, and consequent diminution of 

 circumference since it has had a definite solid 

 crust on which water might condense from the 

 vaporous atmosphere into the oceans. The 

 age of an earth thus limited has greatly 

 reduced the estimates in vogue by the follow- 

 ers of Hutton and Lyell, even though its 3'ears 

 are still to be counted by millions. Its contrac- 

 tion from cooling has also been pronounced 

 insufficient to produce the observed structure 

 of mountain ranges in the wa} r that filie de 

 Beaumont had suggested. Strongly contrasted 

 with these assumptions and their legitimate 

 results are the conclusions reached by Ritter. 

 His original papers were published in Poggen- 

 dorff's ' Annalen,' and have received an approv- 

 ing review from so trustworth}- a physicist as 

 Zoppritz. Giinther quotes largety from the 

 latter. We cannot here do justice to the hy- 

 pothesis, for it would need a somewhat delib- 

 erate statement to make it clear. Excessively 

 dense vapors, probably dissociated from their 

 ordinar} r combinations, and existing at tem- 

 peratures high above their ' critical point,' are 

 supposed to occupy the earth's centre ; and 

 from these there is a gradual transition to the 

 solid superficial crust. The cooling of such a 

 central mass follows a paradoxical law, — the 

 more heat it loses, the hotter it becomes, — and 

 so the supply of interior heat is long main- 

 tained, and the time allowed for geological 

 processes is lengthened. Moreover, the con- 

 tractional theory here finds a cause for all the 

 diminution of interior volume demanded by 

 the wrinkling of the crust in mountain ranges. 

 Altogether, while the venturesome hypothesis 

 is very far indeed from any thing like dem- 

 onstration, its consideration is profitable if it 

 prevent our settling down prematurely to a 



fixed belief concerning the condition of the 

 earth's interior. 



We shall wait impatiently for the second 

 volume of the work, in which the physics of 

 the air and sea will be discussed ; and it will be 

 particularly interesting to see what treatment 

 so learned an author gives to the physical 

 geography of the land. 



ROMANES' RESEARCHES ON PRIMI- 

 TIVE NERVOUS SYSTEMS. 



All who are interested in the physiology of 

 the nervous system in lower animals will find 

 in this volume a most useful popular contribu- 

 tion to this subject. The book, as the author 

 states, is restricted to experiments made in 

 his own researches ; but these are so numer- 

 ous and varied that it will be found to contain 

 a summary of the most important results in 

 this line of investigation which are at pres- 

 ent known. 



' Do the} 7 feel ? ' and ' Have they senses ? * 

 are questions which are very naturally asked 

 by any one who watches the varied movements 

 of the jelly- fishes, star-fishes, and sea-urchins. 

 A natural credulity prompts one to question 

 whether the medusae, whose bodies contain 

 over ninety-eight per cent of water, have a 

 nervous s} T stem, and organs of special sensa- 

 tion. Twenty-five 3'ears ago, science would 

 have given a very unsatisfactory answer to 

 these questions ; but to-day we have a very 

 accurate knowledge of the anatomy of these 

 structures. With this advance in anatomical 

 knowledge, physiological research has kept 

 pace ; and certainly no one has done more than 

 Romanes in this kind of research. Thanks 

 to these advances, we can now reply to our 

 questioner with more confidence than formerly. 

 These animals not only feel, but also have 

 special organs of sight, hearing, and probably 

 smell. 



The author puts the anti-vivisectionists in a 

 receptive frame of mind for the work which 

 follows hy declaring, in the introduction, that 

 his experiments on living animals involve no 

 pain, and that the " consciousness which is 

 present must be of a commensurately dim and 

 unsurTering kind." 



The work is mainly taken up by experi- 

 ments in excising portions of the body, and 

 noting the effects on the movements of the 

 animal. Many very interesting experiments 



Jelly-fish, star-fish, and sea-urchins : being a research on 

 primitive nervous systems. By Gr. J. Romanes. New York, 

 Appleton, 1885. (International scientific series.) 12+323 p., 

 illustr. 8°. 



