Proportion of Bromine in the Waters of different Seas. 323 



gives in the gallon 72 grains of sulphate of lime, and 128 

 grains of sulphate of soda; the second by Dr. Thomson, 

 which represents the same quantity as containing only 34* 

 grains of the former salt, and 20 of the latter*; whilst the 

 latest of all, that of Dr. Ure, states the entire absence of all 

 sulphuric salts whatsoever. The quantit}' of saline matter is 

 also stated very differently by the three analysts. 



With regard to the quantity of bromine present, my estimate 

 in 1829 was 4*68 grains in the gallon. Dr. Ure's in 1834-, 

 6 grains, which is perhaps as near a correspondence as, un- 

 der all the circumstances, can be expected. 



With regard to the indirect method of calculating the pro- 

 portional quantities of bromine and chlorine intermixed, which 

 Dr. Ure has adopted, I may remark, that the very same was 

 proposed by me in an Essay on the Atomic Theory, which 

 1 published in the year 1831, (see page 89 of that work,) and 

 that I have even given in page 92, a table of the relative pro- 

 portions of bromine and chlorine in a given quantity of the 

 silver precipitate, which, if read backwards, will be found 

 to correspond with that given by Dr. Ure in his late paper, 

 allowance being made for the slight difference in the atomic 

 weight of bromine in my calculation and in his. 



It is on the above principle that I had begun to calculate 

 the proportion of bromine present in the waters of different 

 seas; and as the opportunities for obtaining sufficiently large 

 quantities occur but rarely, I may take this occasion of men- 

 tioning, that a sample of sea water taken just outside of the 

 harbour of Marseilles appeared to contain a larger proportion 

 than that of the British Channel off* Cowes. 



The latter I had estimated in my Memoir in the Transac- 

 tions already referred to at about 1 grain in the gallon, but 

 in 1832 I calculated its amount by the method just alluded 

 to at only 0*915 of a grain; whilst in the water of Marseilles, 

 by a similar process, I was led to estimate it at 1*26 of a grain. 

 Yet this did not appear to depend upon a difference in the 

 relative saltness of the two seas, for in the Marseilles water 

 the proportion of salt to water was 3*5 per cent., and in that 

 from the English Channel 3*7. 



Neither must it be inferred that the water of the Mediter- 

 ranean, generally speaking, is richer in bromine than that of 

 the Atlantic, for I have found that some which I lately ob- 

 tained in the Bay of Naples corresponded almost exactly in 

 this respect with that formerly taken from the neighbour- 

 hood of Portsmouth. 



* As quoted in Cubitt's Essay on the Mineral Water of Ashby-de-la- 

 Zouch. 



2T2 



