October 9, 1896.] 



SCIENCE. 



537 



Dr. Herrick has not expressed disapproval of 

 the destructive methods of ' lobster-hatching ' 

 that have been practiced in certain hatcheries 

 for several seasons past. 



The subject of molting and the function of the 

 gastroliths are exhaustively treated, the litera- 

 ture reviewed, erroneous ideas corrected, and 

 many interesting observations recorded. 



In Chapter IV. , on the Regeneration of Lost 

 Parts, we read, "the new limb appears to arise 

 mainly by growth of the connective-tissue cells 

 already present in the stump;" and, further on, 

 "the fibrous tissue becomes gradually differenti- 

 ated into the muscles, blood-vessels and nerves, 

 AS in an embryo." It is unfortunate that fig- 

 ures are not given illustrating this method of 

 regeneration. The sections on Variation will 

 supply valuable material for one interested in 

 the lines of investigation outlined by Bateson. 



Chapters XI. -XIII. deal with general ques- 

 tions of crustacean development and larval life, 

 and are excellently illustrated by prints and 

 colored plates. 



We may add in concTusion that, from the 



breadth of the field covered. Dr. Herrick's 



paper will be frequently consulted, not only 



by those devoted to artificial fish-culture, but 



"by working naturalists, whether embryologists, 



physiologists or students of variation. 



H. C. BuMPUS. 

 Brown University. 



isopentane and hexane. 

 The Thermal Properties of Isopentane. By 



Sydney Young, D. Sc, F. R. S., University 



College, Bristol. (Communicated to the 



Physical Society of London.) 



The isopentane employed in this research 

 was procured from Kahlbaum, of Berlin; the 

 substance is obtained as a bye-product in the 

 manufacture of amylene from amyl alcohol by 

 the action of zinc chloride. The isopentane 

 was purified by repeated agitation with con- 

 centrated sulphuric acid and with a mixture 

 of sulphuric and nitric acids and by subsequent 

 fractional distillation. 



The vapor pressures were determined at tem- 

 peratures from — 30° to the critical point, 

 187.8°; the orthobaric volumes of a gram of 

 liquid from 0° and of saturated vapor from 10° 



to the critical point; and the volumes of liquid 

 and of unsaturated vapor between wide limits 

 of temperature and pressure. 



The experimental methods employed are de- 

 scribed in the original paper and, in regard to 

 pressure, the error due to the vapor pressure of 

 mercury is fully discussed. The volumes of a 

 gram of liquid and vapor were plotted against 

 the pressure and from the isothermals isochors 

 were constructed; it was found that at large vol- 

 umes and just about the critical volume the iso- 

 chors were straight, at any rate within the limits 

 of experimental error, but that at volumes smal- 

 ler than the ci'itical volume the values of -^ 



dt 



increased slightly with rise of temperature, 

 whilst at volumes greater than the critical 

 volume they diminished slightly with rise of 

 temperature. 



The formula p=bT — a at constant volume 

 (Ramsay & Young, Phil. Mag., 1887, 435, c/, 

 Amagat, Compt. Rend., 94, 847), is therefore 

 not quite, though very nearly, ti'ue for isopen- 

 tane, and the results seem to confirm the con- 

 clusion arrived at by Amagat in the case of the 

 substances examined by him that the values of 

 h are not absolutely constant. 



Values of h and 



10,000 



and of a and 



101" 



bv av'' 



for volumes of a gram from 1.58 to 4000 cub. 

 cms. are given in the original paper. 



The absolute temperatures (boiling points) 

 and molecular volumes of liquid and saturated 

 vapot were read from the curves at pressures 

 ' corresponding ' to those adopted in previous 

 papers on the ' Generalizations of Van der 

 Waals regarding Corresponding Temperatures, 

 Pressures and Volumes,' (Phil. Mag., Feb., 

 1892, 153 ; Jan., 1894, 1; Trans. Chem. Soc, 

 63, 1191) and the ratios of the temperatures 

 and volumes to the critical constants were cal- 

 culated. The ratios prpve that isopentane be- 

 longs to Group I in the classification of sub- 

 stances previously adopted (Phil. Mag., Jan., 

 1894, 1). 



The ratio of the actual to the theoretical 

 density at the critical point, 3.73, agrees well 

 with the ratios for the other members of Group 

 I (3.65 to 3.83), and with that for carbon diox- 

 ide (3.62) deduced from Amagat's observations. 



