CHEMISTEY OF NATURAL WATEES. 



179 



comparison. It shows not only the average composition of the great bulk 

 of the waters of the globe, but illustrates one of the most important stages 

 in the history of natural waters. 



Comparison of Ihe means of all regions of the ocean (German Ocean, Kattegat, Baltic, Mediterranean, and 



Black Sea excepted). 



[Expressed in parts per thoasand.] 



It is evident,]}' difficult, if not impossible, to obtain an accurate average 

 of the composition tif the ocean in all latitudes and at all depths, but a con- 

 venient approximation to the truth may be reached The mean of 34.404 

 parts per thousand, given in the above table, is the result of a very large 

 number of analyses, but includes regions of high northern and high south- 

 ern latitude, where the sea must be somewhat affected by the melting of the 

 great glaciers of these regions. It seems questionable, therefore, whether 

 the mean given above is high enough to bo taken as the average salinity of 

 the ocean. Leaving out the analyses of the waters of Davis Strait and of the 

 South Polar Seas, we obtain a general average of 35.101. From 134 analy- 

 ses of waters from various parts of the open ocean, given in Roth's Chem- 

 ical Geology, the general average of 34.957 parts per thousand was ob- 



