1889-90.] Dr J. Murray & Mr R. Irvine on Coral Reefs. 87 
it consisted principally of carbonate of lime, as shown by the follow- 
ing analysis : — 
Precipitate Ten Days after the first one above noted. 
Water and organic matter, . . . . 20 ’2 5 
Carbonate of lime, . . . . . 75*35 
Carbonate of magnesia, ..... 1*02 
Phosphate of magnesia, . . . . . 3*38 
Ammonia, ....... (none) 
100*00 
Examined with the microscope, the precipitate was seen to consist 
of the characteristic crystalline forms of carbonate of lime. It 
effervesced freely with acids. The first precipitate (seven days) 
weighed 2’37 grammes; the second (seventeen days), 2-75 grammes 
— that is, 5*12 grammes in all. Thus after adding the carbonate of 
lime in solution, present in the filtrate, there is practically enough 
lime in these precipitates to account for all the sulphate and car- 
bonate of lime present in the sea water used. In other words, this 
reaction had removed all the soluble calcium salts from the sea 
water, principally as more or less insoluble crystalline carbonate. 
Experiment V. An experiment was made with a solution of sulphate 
of lime of the same strength as present in sea water. 500 c.c. of 
this solution was mixed with 100 c.c. of urine under the same condi- 
tions as in the previous experiment (IV.) ; after eleven days the 
precipitate was collected, and was found to contain 51 per cent, of 
carbonate of lime. This, after adding the carbonate of lime in 
solution in the filtrate, accounted for all the lime present in the 
original solution of sulphate of lime made use of. 
Experiment VI. In this experiment an attempt was made to imitate 
the conditions occurring in nature as nearly as possible. Nine small 
crabs, weighing in all 1 1 ounces, were placed in a shallow glass vessel 
containing 2 litres of ordinary sea water, and were fed on mussel 
flesh. The water was never renewed nor aerated, the effete matters 
passing into it. At the end of fourteen days all the crabs had died, 
and were removed. The w’ater being then in a putrid condition, it 
was set aside for about three weeks at a temperature ranging from 
70° to 80° Falir. All the conditions of the last two experiments 
