HYDROGRAPHY. 



85 



indicates the amount of nitrogen in cubic centimetres — reduced to o° and a pressure of 760 mm. — t 

 that is contained in one litre of sea-water. In the fourth and fifth columns are the two differences 

 c — a and c — b. Next is entered the temperature of absorption determined by the observed amount of 

 nitrogen according to Hamberg's table, and the difference is noted between the observed temperature 

 and the temperature of absorption found in this manner. 



Under 2 is entered in the first column, the observed amount of oxygen — reduced to 

 o° and 760 mm. — which is contained in one litre of sea-water. In the second colume, e means the 

 value adopted by the quantity N , X when sea-water is saturated with asmospheric air under the 

 temperature for the time being. The values that are entered, have been determined by interpolation 

 in Dittmar's table (Report on the scientific results of the voyage of H. M.S. Challenger, Physics & Chemistry, 

 volume 1 page 224). In the third colum, f means the value of ' computed by means of the observed 



amount of oxygen and nitrogen. Finally in the fourth column, the difference f—e is noted. 



Under C0 2 is entered in the first column, the amount of carbonic acid found, which, expressed 

 in cubic centimetres and reduced to o° and 760 mm. is contained in 1 litre of sea-water; in the second 

 column, under A, is entered the alkalinity, expressed by indicating the number of cubic centimetres 

 of carbonic acid required to combine the quantity of alkali which is contained in 1 liter of sea-water 

 in the form of neutral salts. 



In the column for the quantity and nature of the Plankton, A. means animal Plankton, 

 V. vegetable Plankton, Pk. peridiueer containing chromatophores, Pn. peridineer not containing chromato- 

 phores. The cipher before the species of the plankton indicates the proportion of quantity in such a manner, 

 that 1 means that the respective species of plankton only appeared singly in the examined sample; 2 that 

 it appeared rather frequently ; 3 generally, and 4 that it was present in so large a quantity as to characterise 

 the sample. These indications of quantity are all relative, and it is only in a few cases that by a remark 

 anything has been said about the absolute quantity, such as for inst, abundantly, exceedingly scarce, etc 



