262 Dr. Stenhouse on the occurrence of Mannite in the 



First. A deposit, chiefly of sulphate of lime, from, as it ap- 

 peared, a chloride of calcium vat, and found it to contain 

 fluorine, though in small quantity. As it was suggested to me, 

 however, that glass retorts used for the distillation of hydro- 

 chloric acid have been known to be thereby corroded, I did 

 not attach much weight to the result, although I drew en- 

 couragement from it. 



Second. A deposit formed in a wooden conduit pipe in a 

 coal mine, procured for me by my friend Dr. Falconer, and 

 found it to contain a still greater proportion of fluorine than 

 the former. 



Third. A stalactitic deposit, said to have been formed in an 

 aqueduct in France. It was of a pure white colour, and made 

 up of very thin and scaly concentric layers, being at the same 

 time very incompact : it contained no fluorine. 



Fourth. A stalactitic deposit from a cave in old red sand- 

 stone, furnished to me by Mr. Arrott, to whom for this and 

 for other assistance in my investigations I am much indebted : 

 this I found to contain fluoride of calcium to the extent of 

 about 9 per cent. The stalactite consisted chiefly of carbo- 

 nate of lime. 



Fifth. The crust formed on the inside of a kettle used for 

 the boilina: of water : this I found to afford faint but distinct 

 proof of the presence of fluorine. 



Lastly. A fragment of a vein of sulphate of barytes found 

 in the sandstone above mentioned. This also contained fluo- 

 rine, though in much less proportion than the stalactite of the 

 fourth experiment. 



The above are the only substances, sufficiently diverse in 

 their origin, which I have had an opportunity of examining, 

 and the facts I have elicited from them seem to confirm the just- 

 ness of my theory of the prime sources of fluorine in bones. 

 It follows, as a necessary corollary, that it exists in most if 

 not all vegetables, though perhaps in minuteness of quantity, 

 that may enable it often to elude detection. 



XLIII. On the occurrence of Mannite in the Laminaria sac- 

 charina and other Sea-weeds. By John Stenhouse, 

 PA.D.* 

 IVTORE than thirty years ago the Laminaria saccharinaiWith 

 •^^■*- some others of our commonest sea- weeds, were examined 

 by Vauquelin, who detected in several of them a sweet-tasted 



* Communicated by the Chemical Society; having been read May 6, 

 1844. 



