October 18, 1901.] 



SCIENCE. 



613 



which deserve special mention are Nos. 16 

 and 17, from which the position of any of the 

 five brighter planets may be determined for a 

 number of years ; No. 23, which ingeniously 

 illustrates the tide-raising forces ; No. 54, illus- 

 trating the moon's rotation ; No. 121, illustrat- 

 ing the determination of parallax of the fixed 

 stars. 



Of the many apt illustrations contained in 

 the book, the following, page 121, is one of the 

 best : "Every such timepiece, whether it be of 

 the nutmeg variety which sells for a dollar, or 

 whether it be the standard clock of a great na- 

 tional observatory, is made up of the same es- 

 sential parts which fall naturally into four 

 classes, which we may compare with the de- 

 partments of a well-ordered factory : I. A time- 

 keeping department, the pendulum or balance 

 spring, whose oscillations must all be of equal 

 duration. II. A power department, the weights 

 or main spring, which, when wound, store up 

 the power applied from outside and give it out 

 piecemeal as required to keep the first depart- 

 ment running. III. A publication department, 

 the dial and hands, which give out the time 

 furnished by department I. IV. A transporta- 

 tion department, the wheels, which connect 

 the other three and serve as a means of trans- 

 mitting power and time from one to the other. 



"The case of either clock or watch is merely 

 the roof which shelters it, and forms no de- 

 partment of its industry. Of these depart- 

 ments the first is by far the most important, 

 and its good or bad performance makes or 

 mars the credit of the clock." 



The last chapter, growth and decay, de- 

 serves special mention. It is a clear, philo- 

 sophic treatment of the best theories of si- 

 dereal evolution, and although not out of place 

 in a high-school text, it might well form a part 



of a larger treatise. 



Sidney D. Townlby. 

 University of California, 

 May 1, 1901. 



SCIENTIFIC JOURNALS AND ARTICLES. 



TniE Journal of Physical Chemistry, June, 1901. 

 ' The Theory of Electrolytic Dissociation as 

 viewed in the Light of Facts recently ascer- 

 tained,' by Louis Kahlenberg ; ' On the Gener- 



alization of Clapeyron's Equation,' by Paul 

 Sorel ; 'On the Phase Rule,' by Paul Sorel. 

 This paper by Dr. Kahlenberg demands more 

 than passing mention. Since its enunciation 

 by Arrhenius in 1887, the theory of electro- 

 lytic dissociation has received a recognition 

 which has rarely been accorded a scientific 

 theory in so short a time, and few theories 

 have been so productive of results. Unhesitat-' 

 ing assent has been by no means accorded it by 

 many, especially of the older, chemists, but few 

 attempts have been made to reveal its weak- 

 nesses experimentally. Dr. Kahlenberg, him- 

 self a pupil of Ostwald, has been one of the few 

 who have from time to time called attention to 

 experimental facts which were not in accord 

 with the theory. In his present paper, the 

 author first details a large amount of experi- 

 mental work on the electrical conductivity of 

 solutions at low and at high temperatures, and 

 on molecular weight determinations by boiling 

 point and cryoscopic methods, in solutions of 

 gradually increasing strength, in which is shown 

 often a great discrepancy between the results 

 and those required by the dissociation theory. 

 He then proceeds to discuss at length these and 

 many other failures of the theory, drawing the 

 conclusion that the theory is applicable to a de- 

 cidedly limited class of solutions. The true 

 nature of solutions must be reached by a study, 

 not of those extremely dilute, but first of the 

 concentrated solution, approaching the dilute 

 solution as a limiting case. In conclusion, he 

 says: "It must be fully and freely admitted 

 that the dissociation theory has done much good 

 in stimulating research in many lines. It has 

 been fruitful in proportion to the amount of 

 truth contained in it. Like other theories 

 founded upon too narrow a basis of induction, 

 it has gradually been outgrown — the facts are 

 too much for it. It would be difficult of course 

 to say of any theory — even of one long ago dis- 

 carded — that it is entirely worthless, and so the 

 writer has no inclination to make such a state- 

 ment concerning the dissociation theory. * * * 

 It is solely because of the rapid growth of the 

 erroneous idea that the deductions drawn from 

 the indiscriminate application of the simple gas 

 equation to solutions and from the notion that 

 all well-known facts harmonize with the theory 



