Report of the Kew Observatory Committee. 161 



filtration through, sand impregnated with vegetable growth, and after 

 adding algae to the water, the nitrites are increased. The growth of 

 larvae in a water is as a rule accompanied by an increase of nitrites, 

 though the nitrification does not seem to be increased on the addition 

 of either ammonium salts or nitrates to the water, or on fouling the 

 water by animal excretions. 



The arm-lengths of the larvae are not specially affected by vege- 

 table growth, though by water filtered through sand impregnated 

 with algae and diatoms they are somewhat diminished. They are 

 considerably increased on development of the larvae in water purified 

 by being kept in darkness, and in aerated water. They are greatly 

 diminished in water previously heated to 100, but not in that heated 

 to from 50 to 77. In water exposed to sunlight they are also 

 diminished. They are increased in water fouled by most animals 

 and by dead Echinoids, but in that fouled by living Echinoids are 

 diminished. 



During a period of seven months the specific gravity of the 

 Aquarium water was found to vary from 1-02859 to T02964 at 

 15*56 C. The specific gravity was on an average about 0'00040 

 greater than that of the open sea water. The free ammonia varied 

 from 0*185 to 0*350 milligram per litre, and the albuminoid from 

 0-111 to 0-182 milligram, 



Report of the Kew Observatory Committee for the Year 

 ending December 31, 1897. 



The operations of The Kew Observatory, in the Old Deer Park, 

 Richmond, Surrey, are controlled by the Kew Observatory Committee, 

 which is constituted as follows : 



Mr. F. Galton, Chairman. 



Captain W. de W. Abney, C.B., 



E.B. 



Prof. W. G. Adams. 

 Captain E. W. Creak, R.N. 

 Prof. G. C. Foster. 

 Prof. J. Perry. 

 The Earl of Rosse, K.P. 



VOL. LXI1T. 



Prof. A. W. Riicker. 



Mr. R. H. Scott. 



Mr. W. N. Shaw. 



Lieut. -General Sir R. Stracher, 



G.C.S.I. 

 Rear Admiral Sir W, J. L. 



Wharton, K.C.B. 



