732 



SCIENCE 



[N. S. Vol. XLII. No. 1090 



this volume and illustrated in satisfactory 

 form. Fifteen British naturalists have con- 

 tributed papers, and the book is perhaps the 

 most complete treatise on the Antarctic verte- 

 brate fauna yet published. 



The birds, seals, whales and fishes, are fully 

 illustrated with excellent plates, and much 

 space is given to anatomy, osteology and em- 

 bryology; while the economic aspects of the 

 fauna are not neglected. Papers on the tuni- 

 cates and Cephalodiscus are included. A few 

 forms obtained on the voyage but which are 

 not strictly Antarctic are incidentally noticed. 

 Altogether the members of the staff and the 

 contributors to the explorations and publication 

 of the results may justly congratulate them- 

 selves on the appearance of this handsome vol- 

 ume at a time when general attention is un- 

 fortunately diverted from matters of science 

 and focused on the preservation of the empire. 

 Wm. H. Dall 



SPECIAL ARTICLES 



THE CALCULATION OF TOTAL SALT CONTENT AND OF 



SPECIFIC GRAVITY IN MARINE WATERS^ 



To the investigator engaged in biological 

 studies on marine problems, it is often desira- 

 ble to ascertain the concentration of sea-water 

 in terms capable of correlation with life phe- 

 nomena. Such concentration records usually 

 take the form of density determinations made 

 with some standard type of densimeter at the 

 prevailing temperature. These density read- 

 ings, while useful as physical records, are not 

 directly adapted to physiological use. The 

 quantity of salts present in sea-water is a term 

 which can be so utilized and it becomes espe- 

 cially valuable in view of the fact that the 

 proportion of constituents has been shovm to 

 vary but slightly, the concentration only being 

 subject to considerable variation. By means 

 of the Challenger proportions worked out by 

 Dittmar^ any total salt content can be resolved 

 into its chief constituent parts. These pro- 

 portions are as follows: 



1 Published by permission of the Secretary of 

 Agriculture. 



2 Dittmar, Challenger Eeports, Physics and 

 Chemistry, Vol. 1, Part 1, p. 138. 



Per Cent. 



NaCl 77.758 



MgCL 10.878 



MgSO, 4.737 



CaSOj 3.600 



K,SOi 2.465 



MgBr, 0.217 



CaCOj 0.345 



It has been shown that the total salt con- 

 tent is directly related to the specific gravity 

 and that one may be calculated from the other. 

 Specific gravity determinations are made with 

 reference to different standard temperatures. 

 Frequently density readings are made with the 

 temperature indicated in Fahrenheit units. 

 These are usually referred to 60° F. as a stand- 

 ard temperature, and the observed density is 

 reduced to 60° F., sp. gr. 60° F./60° F. This 

 is easily done by means of Libbey's tables.^ If 

 the observed temperature is below 60° F. sub- 

 tract the observed degrees of temperature from 

 60, multiply this difference by the correction 

 found in the table opposite the observed tem- 

 perature and subtract the product from the 

 reading to be corrected. If the density is ob- 

 served at a temperature above 60° F. ascertain 

 as before the number of degrees of difference 



3 Libbey, "William, ' ' Physical Investigations off 

 the New England Coast," Bull. IT. S. Fish Com- 

 mission, 9, pp. 397-398 (for 1889). 



