12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 56 



over 400 miles inland, appears to receive the greater part, if not all of its 

 salt from dust-laden winds which, during the four hot, dry months, sweep 

 over the plains between it and the arm of the sea known as the Kann of 

 Cutch. Analyses of the air during the dry season, showed a quantity of 

 salt so carried which amounted to at least 3000 metric tons over the 

 Sambhar lake annually, and 130,000 tons into Kajputana. These quanti- 

 ties are sufficient to account for the accumulated salt of the lake, which 

 the authors were unable to explain in any other way. 



Examples like this of the Sambhar lake are of course exceptional. In a 

 rainy region salt dust is quickly dissolved and carried away in the drain- 

 age. Only in a dry period can it be transported as dust from its original 

 point of deposition to points much further inland. It appears, however, 

 that some salt is so withdrawn, at least for an indefinitely long time, from 

 the normal circulation, and should, if it could be estimated, be added to the 

 amount now in the ocean. Such a correction, however, would doubtless 

 be quite trivial, and, therefore, negligible; and the same remark must 

 apply to all the visible accumulations of rock salt, like those of the Stass- 

 furt region, which were once laid -down by the evaporation of sea water. 

 The saline matter of the ocean, if concentrated, would represent a volume 

 of over 4,800,000 cubic miles; a quantity compared with which all beds 

 of rock salt become insignificant. 



. But although the visible accumulations of salt are relatively insignifi- 

 cant, it is possible that there may be quantities of disseminated salt which 

 are not so. The sedimentary rocks of marine origin must contain, in the 

 aggregate, vast amounts of saline matter, widely distributed, but rarely 

 determined by analysis. These sediments, laid down from the sea, cannot 

 have been completely freed from adherent salts, which, insignificant in a 

 single ton of rock, must be quite appreciable when cubic miles are con- 

 sidered. The fact that their presence is not shown in ordinary analyses 

 merely means that they were not sought for. Published analyses, whether 

 of rocks or of waters, are rarely complete, especially with regard to those 

 substances which may be said to occur in " traces." 



It is perhaps not possible to estimate the quantity of this disseminated 

 salt, and yet a maximum limit may be assigned to it. In a former pub- 

 lication ^ it was shown that 84,300,000 cubic miles of the average igneous 

 rock would, upon decomposition, yield all the sodium of the ocean and the 

 sedimentaries. This estimate involved the maximum, not the mean 

 salinity of the ocean, and also a different value for the mass of the latter 

 from that now adopted. In order to revise the estimate, which must be 

 considerably reduced, it is desirable first to consider the average composi- 

 tion of the two classes of rocks, especially since the data are applicable to 

 other phases of the discussion than that now under consideration. 



1 Data of Geochemistry, pp. 28-29. 



