GEOPHYSICAL LABORATORY. 173 



(32) The dissociation of calcium carbonate below 500°. R. B. Sosman, J. C. Hostetter, 



and H. E. Merwin. J. Wash. Acad. Sci., 5, 563-569 (1915). 



Pure lime, CaO, is obtainable in two forms. The first, which is probably 

 amorphous, results from the dissociation of CaCOs at low red temperatures. 

 On heating for a considerable time at higher temperatures, it changes gradually 

 into the cubic crystalline lime of refractive index 1.83. The latter forms 

 directly from silicate melts or from fused calcium nitrate, and is the stable 

 form at high temperatures. There are indications that it has an inversion- 

 point (perhaps similar to the inversion between high- and low-temperature 

 quartz) between 400° and 430". 



The porous lime unites very readily with dry carbon dioxide, and the com- 

 pound dissociates readily with rising temperature. The crystalline lime unites 

 very slowly with dry carbon dioxide. The crystalline forms of calcium car- 

 bonate dissociate very slowly at low temperatures, and the rate does not seem 

 to be hastened by the presence of FegOs or of CaO. Aragonite is transformed 

 into calcite within an hour at 425° in the vacuum furnace. The dissociation 

 pressures of crystalline calcium carbonate at 400° are of the order of magnitude 

 of 0.003 to 0.009 mm. 



(33) The constituents of portland cement clinker. G. A. Rankin. Concrete-Cement Age, 



6, 55-63 (1915). 



Reprinted from "The constitution of portland cement clinker" (J. Ind. Eng» 

 Chem., 7, 466-474, 1915). Reviewed under No. 17 above. 



(34) Present condition of the volcanoes of Southern Italy. H. S. Washington and Arthur 



L. Day. Bull. Geol. Soc. Am., 26, 375-388 (1915). 



The volcanoes Vesuvius, Etna, Vulcano, and Stromboli were visited in 

 the summer of 1913 and their condition of activity at that time described. 

 Vesuvius showed signs of a renewal of activity, which was to be expected after 

 the exceptionally long interval of repose since the last great eruption of 1906. 

 A descent to the bottom of the crater was made in June, which permitted some 

 detailed observations at the active vent. Etna was found to be in a moder- 

 ately active condition, with minor solfataric and strombolian outbursts. 

 The large bocca of 1911 has greatly increased in diameter. It appears to be 

 eating its way into the main crater, and it is probable that when this hap- 

 pens an eruption may be expected. Stromboli was in its normal active condi- 

 tion. Five vents in the crater were observed, each differing from the others 

 in the character of its activity. Vulcano was in the same solfataric condition 

 which has prevailed since the last eruption in 1888-89. 



Many samples of gases and salts were collected, especially at Etna and 

 Vulcano, which are now being investigated. It is noteworthy that, at 

 Vulcano, the salts are practically free from chlorides, and that the amount of 

 boric acid has greatly decreased since the last eruption. A large collection of 

 rocks from all the volcanoes was also made, which are to be studied later. 



