298 Br. R. D. Thomson, on the [April 



canal, and, as the solution of the difficulties of the inquiry 

 are very closely connected with the geological nature of the 

 country, a few words upon the subject may not be out of 

 place here. The whole of the soil which covers the island 

 being extremely thin, it is obvious that the bottoms of the 

 tanks, which are several feet below the level of the sur- 

 rounding surface, must consist of solid rocks, and the mar- 

 gins being fortified with artificial building, we see that the 

 water can have little opportunity of acting upon the soft 

 soil, so as to produce a mixture of the earthy particles, and 

 hence, that the substances of a saline nature in solution 

 must derive their origin from the disintegrated rocky mass. 

 A muddiness, however, generally exists in these waters, 

 which appears to be produced by the agitation excited by 

 the natives entering for the purpose of carrying off the 

 water, and for bathing ; but the proportion of mechanical 

 mixture thus occasioned does not necessarily exist in general 

 to any greatly appreciable amount, because, when the cause 

 of excitement is removed, the commingled matter speedily 

 subsides. The temperature is always equal or above that 

 of the atmosphere, and in the dry season may be rated at 

 from 80° to 86°. It affords the following results with 

 re-agents : — 



1 . A solution of acetate of lead produces a copious white 

 flocky precipitate. 



2. A slight precipitation with oxalate of ammonia. 



3. A muddiness with muriate of barytes. 



4. A milkiness with lime water. 



5. A precipitate with nitrate of silver. 



From these facts we may deduce that the water contains 

 in solution (1.) a quantity of vegetable or animal matter. 

 Judging by the eye of the relative proportions of the preci- 

 pitate by acetate of lead in the Thames and Bombay water, 

 we should be inclined to refer the maximum to the former, 

 and no one will affirm that the water procured from the 

 Thames is pernicious to health. 

 (2.) Small quantities of 

 Chloride of sodium 

 Sulphate of lime 

 Carbonate of lime. 

 The animal and vegetable matters are derived, there can 



