10 SMITHSON^IAN MISCELLANEOUS COLLECTIONS VOL. 56 



quantities of sodium chloride. On the other hand, a large part of the 

 strata have been exposed to the leaching of vadose waters for so many mil- 

 lion 5rears that it is difficult to imagine how they can still retain any secu- 

 lar salt. The subject of juvenile sodium chloride is perhaps even more 

 obscure. That many volcanic springs and many springs originating far 

 below the stratified rocks bring ready-made sodium chloride to the surface 

 is certain. Even where there are now no springs of this description, there 

 may have been such at comparatively recent geological dates. 



That sedimentary rocks do actually carry large quantities of dissem- 

 inated salt seems to me fully established by the recent work of the hydrol- 

 ogists, in particular that of Mr. Dole. They have left no doubt that waters 

 flowing through stratified rocks carry far more chlorine than those from 

 massive drainage basins, and it is be3^ond question that this excess of 

 chlorine is combined with alkalis. I have only very lately learned to ap- 

 preciate the facts, and have previously erred in supposing the disseminated 

 salt of the sedimentaries unimportant. 



There seems to me the best reason to suppose that the origin of dis- 

 seminated salt in strata is open to investigation. Careful chemical work 

 on suificiently numerous specimens should show whether the compounds 

 associated wath the salt arc those to be expected from sea-water or those 

 characteristic of deep springs, and at least a rough estimate of the pro- 

 portion of secular sea-salt should be attainable. 



At present I see but one way in which to form any opinion as to the 

 division of the questionable 66 x 10" tons of sodium into secular and 

 juvenile portions. Mr. Clarke has shown that a shell of average igneous 

 rock enveloping the globe and 2050 feet thick would yield all the sodium 

 of the ocean and the unchloridized sodium of the sedimentaries, and this 

 result is confirmed by computation from the magnesium contents. If the 

 continental area has always been as large as now, Clarke's shell would 

 make a continental layer four times as thick, or 8200 feet. Thus if there 

 were no juvenile sodium the total denudation of massive rocks, since the 

 waters under the heaven were first gathered together unto one place and 

 dry land appeared, would slightly exceed a mile and a half. Considering 

 the vast well-demonstrated erosions, this figure is by no means startling. 

 If the whole 66 x lO*' tons were juvenile, the layer would reduce to 60 

 per cent, of 8200 feet, or to 9/10 of a mile, a depth considerably smaller 

 than that of the deepest part of the Grand Canon of the Colorado. As a 

 field geologist I should unhesitatingly reject any train of reasoning how- 

 ever plausible which led to so low an estimate as this of the total denuda- 

 tion. Some juvenile sodium there certainly is, but it seems to me that 

 this must form but a small part of the 66 x lO'' tons. 



To be on the safe side I shall estimate the ase of the ocean on two 



