S96 Scientiftc Intelligence. [May, 



desen»e a separate communication, and on which I may yet take this 

 opportunity of offering some short remarks. In your account of 

 Count Rumford you have omitted to mention the memoirs which he 

 published abroad, and the medal which he entrusted for distribution 

 to the Royal Society. To the last query of M. (p. 314), it may be 

 answered that he will find the subject mentioned at p. 31 of Sii.ith's 

 Optics, and at p. 148 of Dr. Jurin's Essay on Distinct Vision (an- 

 nexed to that work) ; and that a number of curious experiments, 

 wliich give greater precision to the inquiry, will be found in 

 Harris's Optics, and in a paper of Dr. Herschell's in the Phil. 

 Trans, for IJSG (vol. Ixxvi.). 



• N. R. D. 



VIII. Effect of Sulphuric Acid on Agates. 



What can be the reason that agate heated, or rather boiled, in 

 ■concentrated sulphuric acid, becomes in its different layers diffe- 

 rently coloured ; the white strata becoming milk-white, and the 

 greyish ones as black as pitch ? I heard this from Mr. Banks, \\\ 

 Bath, and would not believe it ; but Mr. Banks was so good as to 

 make the experiment in my presence, and I was convinced of the 

 fact. Saxon agate is more affected than the Scotch is : half an 

 liour or one hour is generally suflicient for producing the effect. 

 The colours penetrate to a considerable depth. I think this fact 

 fully merits the attention and investigation of chemists and mine- 

 ralogists. 



GlasgoiD, March 13, 1815. J. HaMEL, M. D. 



IX. Const'itJients of the RiLes Grossularia, [Greeri Goosberry.) 



We know from Scheele that the juice of this fruit contains citric 

 and malic acids. Dr. John lias lately subjected it to a more detailed 

 analvsis. This juice has a greenish, and somewhat thick consist- 

 ence _; but it does not gelatinize when exposed to the air. John 

 could find in it hardly any traces of sugar, and therefore is dis- 

 posed to doubt the possilnlity of converting it into wine ; but this 

 is often and successfully put in practice in this country. Indeed 

 the taste of this gooseberry is very distinctly sweet. The following 

 are the constituents found in this juice by John. 



Much water. A salt with base of magnesia. 



Uncrystallizable sugar. Traces of pliosphatcs of lime 

 -' .Supercitrate of potash. and magnesia. 



Supermalate of potash. Trace of muriate of lime ? 



Supercitrate of lime. A little pliosphate? of iron. 



Supermalate of lime. Ammonia, probably comt)ined 

 A little resin. with citric and malic acids. 



Prunin or cerasin.* Fibrin. 

 Insoluble modified gum. 



» This is a substance similar to gum in appcirance; but it does mt dissolre i« 

 water, only swelling up and becoming gelatinous inlbat liquid. 



