Apkil 4, 1902.] 



SCIENCE. 



537 



lectures before farmers ' organizations have 

 been delivered since the College was estab- 

 lished, but they certainly number several 

 thousand. In addition to all this, the Col- 

 lege has done a vast work in helping the 

 farmers out of their difficulties by personal 

 correspondence. From five to ten thousand 

 letters per year in answer to questions are 

 written by the staff. This work alone is a 

 great tax upon the College, but the benefits 

 derived are so great that the practice still 

 continues of answering, to the best of our 

 ability, all questions related to agriculture, 

 directly or remotely. 



' ' The Experiment Station, a department 

 of the College of Agriculture, has published 

 196 bulletins, in editions averaging more 

 than 20,000 each, and fourteen annual re- 

 ports. "Wlienever there is a serious out- 

 break of insects or fungi, a specialist is 

 dispatched immediately to make investiga- 

 tions and to help overcome the diffi- 

 culty. * * * 



' ' Agricultural students have gone to all 

 parts of the State and carried with them 

 the light of science to aid the farmer in 

 his arduous and difficult, though inde- 

 pendent and noble, calling. Professors, by 

 their investigations on the diseases that 

 attack grains and fruits and flocks and 

 herds, have saved millions of dollars to the 

 State. The Cornell method of combating 

 the pear-sylla saved over a million dollars 

 to a single county. Methods of orcharding 

 have added noticeably to the prosperity of 

 farmers and fruit growers." 



Cornell UNivERsriY. R- H. Thurston. 



SCIENTIFIC BOOKS. 

 Die heierogenen GleichgeivicMe, vom Stand- 

 punhte der Phasenlehre. Erstes Heft: Die 

 Phasenlehre: Sysieme aus einer Kompon- 

 ente. By H. W. Bakhuis Eoozeboom. 

 Braunschweig, Friedrich Vieweg und Sohn. 

 1901. 14x22 cm. Pp. xiii + 217. Price, 

 paper, 5.50 Marks. 



Every one who lectures on a subject feels 

 the necessity of presenting it, so far as may 

 be, in a systematic, coherent manner. Per this 

 reason we make the 'periodic law' the basis 

 of lectures on inorganic chemistry, while we 

 classify organic substances according to their 

 constitution formulas. In physical chercdstry 

 the order of treatment has been based largely 

 on the physical state of the system, gaseous, 

 liquid or solid. It is an open question 

 whether the orthodox classification is or is 

 not the best in the case of inorganic and 

 organic chemistry; but it is certainly not sat- 

 isfactory for physical chemistry. The ideal 

 classification for this last subject is based on 

 the phase rule of Willard Gibbs and depends 

 primarily on the number of components and 

 secondarily on the degrees of freedom. By 

 the components we mean the substances from 

 which the system can be made, and we classify 

 our material first as one-component, two-com.- 

 pouent, three-component systems, and so on, 

 usually grouping systems containing more 

 than three components under the single head 

 of multi-component systems. We next sub- 

 divide each group according to the degrees of 

 freedom, this depending on the relation be- 

 tween the number of independently variable 

 components and the number of phases. By 

 phases we mean the physically distinct por- 

 tions of the system, such as the solution or 

 liquid phase, the vapor phase, the solid phase 

 or phases. When the only factors to be con- 

 sidered with relation to equilibrium are the 

 pressure, temperature and the relative masses 

 of the components, the state of the system is 

 fixed when there are two more phases than 

 there are components. Such a system is 

 called an invariant system. When there is 

 only one more phase than there are compo- 

 nents, the system is called a univariant sys- 

 tem, and it is said to have one degree of free- 

 dom because the state is not fixed until we 

 settle arbitrarily the value of one of the inde- 

 pendent variables. When the number of 

 phases equals the number of components, the 

 system is a divariant one having two degrees 

 of freedom. Each decrease in the number of 

 phases means an equal increase in the degrees 

 of freedom. 



