92 REPORTS OF INVESTIGATIONS AND PROJECTS. 



Mixtures of alumina and silica have proved unusually difficult to study, 

 on account of the extremely high temperatures at which combination takes 

 place, which carries them out of reach of the more convenient forms of 

 electric furnace and makes the accum.ulation of definite experimental data 

 more difficult and much slower. Inasmuch as a recent paper from this 

 Laboratory on the 'Xime-silica series of minerals"* appeared to upset one of 

 the fundamental assumptions heretofore made regarding the composition of 

 Portland cement, it is hoped that this investigation of alumina and silica may 

 mark the beginning of the acquisition of some positive information upon the 

 character of this most important and useful mineral combination. 



The study of wollastonite and the analogous silicate of magnesia has not 

 only yielded important information regarding the conditions under which 

 these minerals combine, but appears to contain a most interesting example 

 (the first among the minerals) of a eutectic and a solid solution in the same 

 series, probably corresponding to Type V of Roozeboom's theoretical treat- 

 ment of the 2-component series. Diopside is definitely established in its 

 familiar position as a i : i combination of the metasilicates, which combines 

 with wollastonite in the typical eutectic relation and with magnesium meta- 

 silicate in a more complicated fashion, which is not yet entirely established. 

 This is not especially surprising in view of the fact that the study of magne- 

 sium metasilicate published a year agof showed this composition to be capa- 

 ble of existence in four forms in monotropic relation to each other, of which 

 enstatite, the most common mineral of this composition, is not the most 

 stable. It is therefore extremely difficult, in combinations of diopside and 

 magnesium metasilicate, to be quite sure of the degree of stability obtaining 

 in a particular mixture, within the limited time required for a laboratory 

 experiment. 



Published JVork.— The published work of the Laboratory during the year 

 1907 has appeared in the scientific journals under the titles indicated below: 



(i) Bemerkungen iiber die Julius'sche Galvanometeraufhangung. Walter P. While. 

 Ann. d. Phys. (Leipzig), (4), 22, pp. 195-198, 1907. 



A description of a number of proposed modifications of the Julius suspen- 

 sion, a device for mounting galvanometers or other physical apparatus in 

 such a way that it will not be disturbed by vibrations in the building. 



(2) Die Konstanz der Thermoelemente. Walter P. White. Phys. Zeitschr. (Gottin- 

 gen), 8, pp. 325-338, 1907. 



Reprinted in German from "The constancy of thermoelements" (Physical 

 Review, 23, pp. 449-474, 1906) at the special request of the editor of the 

 Physikalische Zeitschrift. In this republication some new matter was added 

 embodying later information upon the same subject. Through increased 

 refinement in the methods of testing the elements, some further disturbing 



*Amer. Journ. Sci., October, 1906, p. 265. 

 t Amer. Journ. Sci., November, 1906, p. 385. 



