319 
1888-89.] Prof. Tait on a Geometrical Problem. 
where a? is to be found from 
Z2-V2 = ®¥_82 
The two values of x 2 have opposite signs. Hence there are two real 
values of x, equal and with opposite signs, giving two real points on 
the sphere. Thus this case of the problem is always possible. 
The Solubility of Carbonate of Lime in Fresh and Sea 
Water. By W, S. Anderson, Chemist at Marine Station , 
Granton. 
(Read May 20, 1889.) 
At Dr Murray’s request, 1 have during the past winter continued 
the investigation of Messrs Irvine and Young on the solubility of 
carbonate of lime in its different forms in sea water (the results of 
which they submitted to this Society in May 1888); and the 
following notes of the work done and the results obtained by 
me, under Mr Irvine’s guidance, in the laboratory of the Marine 
Station, Granton, may be of interest. 
At his request, I have satisfactorily checked the results already 
laid before you. This has also, I understand, been done by Professor 
Thoulet of Haney. 
In that paper special attention was given to the solubility of 
amorphous and artificially crystallized carbonate of lime, and the 
various forms of coral in sea water. 
The later experiments with Iceland spar show it to be much less 
soluble than the above-named forms of carbonate of lime in sea water. 
As shown in the Table, calcite is less soluble in sea water than in 
pure water, the former dissolving of the impalpable powder only 
0*0082 grammes per litre; while distilled water, free from carbonic 
acid, dissolved during the same time 0*0251 grammes per litre 
(more than three times as much). There is hardly any notable 
difference in the solubility of calcite, whether in the form of im- 
palpable powder, or in the condition of coarse powder, or large 
crystals, in sea water ; the solubility being only a trifle less with 
massive than with the more finely divided variety (see Table). 
With distilled water there is a very marked difference, the powdered 
