ABSTRACTS AND DISCUSSIONS OF PAPERS 49 



Discussion r 



Prof. J. P. Iddings heartily approved of the proposition of Professor Daly 

 regarding the systematic surrey of the islands of the Pacific and suggested 

 the desirability of having a properly equipped steamer for carrying out the 

 survey. 



Further remarks were made by Messrs. A. C. Lane and N". L. Bowen, 

 with reply by the author. 



SOME FACTORS WHICH AFFECT THE DEPOSITION OF CALCIUM CARBONATE 



BY JOHN. JOHNSON * 



(Abstract) 



This paper gave a brief discussion of the operation of the inorganic factors 

 which affect the solubility, hence the precipitation of calcium carbonate, and 

 therefore are important in connection with the origin and mode of formation 

 of limestones. Of these factors there are two in particular, namely, the con- 

 centration of free carbon dioxide in the water and the temperature, which 

 exert an influence more far-reaching than has hitherto been generally recog- 

 nized ; indeed, it appears that by considering their effects alone we are enabled 

 to coordinate a large number of the phenomena of the deposition of limestones. 



Presented in abstract extemporaneously. 



Eemarks were made by Dr. A. C. Lane, with reply by the author. 



SPECIFIC WEIGHT OF DRILL CORES 

 BY ALFRED C LANE 



(Abstract) 



It has been found that the specific gravity of drill cores, or volume per cubic 

 foot, can be readily obtained by measuring their dimensions. This can be 

 done to an accuracy of within 1 per cent, in pieces of core over 100 mm. long, 

 without grinding off the ends, by using the micrometer gauge for the diameter 

 and taking the average of six measurements of the diameter and the average 

 of about four measurements of the length made with a finely graduated ruler. 

 Thus, after weighing them, the weight in grams per cubic centimeter or (the 

 same thing) ounces per cubic foot is obtained. Systematic tests seem to show 

 that this may be of considerable practical value, as the variation in one lava 

 flow between the denser, more crystalline, less glassy, and the more glassy, 

 less crystalline, and perhaps more altered upper and lower parts, can be dis- 

 tinctly and continuously followed, even when the amygdaloidal or vesicular 

 structure is not conspicuous. 



Presented in abstract extemporaneously. 



1 Introduced by H. S. Washington. 



