GEOPHYSICAL LABORATORY. 99 



cent alumina, is perhaps the most important one of the series in that it may 

 appear later in the investigation of the Portland-cement portion of the dia- 

 gram. This compound seems to be partly dissociated at its melting-point, so 

 that whatever precautions are taken it never appears absolutely pure. There 

 is always a slight excess of crystallized lime and a corresponding amount of 

 the 52 per cent compound. Prolonged heating at 1,300° causes these excess 

 components to disappear. It is well crystallized and isotropic. All the mix- 

 tures of the series up to about 60 per cent are readily attacked by water and 

 easily dissolved in moderately dilute hydrochloric acid. 



The completion of these two axes of the triangular diagram prepares the 

 way for the investigation of ternary mixtures of these oxides which is now 

 under way. Guarinite and meionite have been prepared synthetically in the 

 course of the investigation. 



Extreme Pressures. — The application of pressures of a magnitude compar- 

 able with that which may have obtained in the interior of the earth was neces- 

 sarily postponed so long as the laboratory remained installed in the Geological 

 survey building on account of the obvious danger of accident attending such 

 experiments. Since the removal to the new laboratory building, attention has 

 again been directed to this question and the development of the necessary 

 plant and methods of measurement placed in the hands of Dr. A. Ludwig, of 

 Dusemond, Germany, who has had unusual experience in this field. A plant 

 is being installed and is now nearly ready for test which is expected to develop 

 measured pressures up to 3,000 atmospheres or more in various gases, in which 

 it is first proposed to repeat the experiments upon the liquefaction of carbon 

 with which Dr. Ludwig's name is already connected ; and afterward, to at- 

 tempt to measure the effect of such pressures upon rock formation, both in 

 the presence of water and without it. Bombs in which compressed water- 

 vapor is made to react on minerals for moderate ranges of temperature have 

 been in successful use for some time.* 



Published Work. — A review of the published work of the year follows. In 

 establishing ourselves in the new laboratory building, considerable attention 

 has been given to the perfection of methods and apparatus, and a number of 

 the papers which follow (Nos. i, 2, 3, 5, and 7) will be found to deal with 

 this phase of the investigation. Nos. 6, 8, and 9 describe apparatus suggested 

 by these studies which finds application outside of the work of this Lab- 

 oratory. 



(i) What is the most important portion of a thermoelement?! (Abstract.) Walter P. 

 W'hite. Phys. Rev. 26, p. 535, 1908. 



Along a thermoelement as ordinarily used, there are three temperature re- 

 gions ; one, fairly constant, at each end, and an intermediate gradient region 



* Annual Report for 1907. 



t Abstract of a paper presented at the Washington meeting of the Physical Society, 

 April 24-25, 1908. 



