158 CARNEGIE INSTITUTION OF WASHINGTON. 



respondinfj; change in the state of volcanic activity within the craters. This is 

 attributed to atmospheric condensation due to the volcanic dust. 



In contrast with previous eruptions, explosive phenomena were not con- 

 spicuous features, though two violent explosions were recorded. This is in 

 accord with an opinion already expressed elsewhere, that Stromboli has 

 recently entered on a new period of increased activity of a kind different from 

 that which has been observed at Stromboli hitherto, and one which should 

 therefore be most carefully and if possible continuously studied. 



(33) On the measurement of temperature in bore-holes. John Johnston and L. H. Adams. 



Econ. Geol., 11, 741-762 (1910). 



A systematic and accurate investigation of temperature gradients within 

 bore-holes is desirable because it would yield information as to the relative 

 heat conductivity of different strata, and there is also reason to believe that 

 it would be of some economic importance. Such an investigation would, 

 however, be of little use unless the accuracy of the observations were better 

 than has hitherto been customary. In this paper the various methods which 

 may be used for the measurement of temperatures in bore-holes are discussed 

 in detail and some of the precautions which must be observed are pointed out. 

 The electrical-resistance thermometer is recommended as the most satis- 

 factory device for such temperature measurements, and some new results 

 obtained with a resistance thermometer are presented. It appears that the 

 mercury thermometer can not yield results with an uncertainty less than 

 ±0.1° C., that it is not absolutely trustworthy unless the temperatures to be 

 measured are higher than the prevailing air-temperature at the surface, and 

 that the attainment of even this accuracy requires an exposure of more 

 than an hour at each horizon. In comparison with this, the accuracy of the 

 electrical thermometer is ten times as good, and the time required for an 

 observation is not over one-third as long; the necessary apparatus is, however, 

 somewhat less easily portable and its operation requires some degree of 

 previous experience with electrical measurements. 



(34) The r61e of inorganic agencies in the deposition of calcium carbonate. John Johnston 



and E. D. WiUiamson. J. Geol., 24, 729-750 (1916). 



Though organic agencies are predominantly responsible for the deposition 

 of calcium carbonate, yet the purely inorganic factors should also be taken 

 into account in discussions of the mode of deposition. In this paper emphasis 

 has been laid on one point which has not received adequate recognition, namely, 

 the concentration of calcium relative to the limiting saturation concentration of 

 calcium carbonate under the particular conditions, or in other words, the 

 relative degree of saturation with respect to calcium carbonate in the ocean. 

 The importance of this factor is obvious if we recollect that the chance of a 

 permanent deposit is, ceteris paribus, greater the more nearly saturated the 

 surrounding water is ; its neglect is doubtless due to the erroneous and mislead- 

 ing statements as to the solubility of CaCOs which have been prevalent. 

 The solubility under specified conditions can now be calculated with the 

 requisite accuracy; it is affected materially by variations of temperature and 

 of concentration of free C'Oa such as occur in nature. For example, a change 

 in the proportion of CO2 in the adjacent air from 3.2 to 3.0 parts per 10,000, 

 or an increase of temperature of 2° C. would result ultimately in the precipita- 

 tion of about 2 grams CaCOj from every cubic meter of a solution saturated 

 with it. Comparison of the solubility as calculated with the available analyt- 

 ical data indicates that the warmer surface layers of the sea are substantially 

 saturated with respect to calcite, and, consequently, that precipitation is to be 

 expected wherever the water is being warmed, or is losing CO2, or both, and 



