1854. ] OF THE ROYAL INSTITUTION. 393 
quality of the wine. You cannot thus tell port from sherry; far less 
good port from bad port. If youlook at the Port table the numbers are 
nearly identical. Mr. Brande’s experiments were undertaken for the 
purpose of saying whether alcohol was added to the wine or not; 
whether it was natural or ‘ fortified.”” It would be as easy to add 
salt to sea-water and then endeavour by chemistry to say which 
salt belonged to the sea-water and which was added. 
In the last Report of the Committee of the House of Commons, 
it is stated that most wine is fortified with ten per cent. of brandy, 
and even as much as one sixth of all the spirit may be intermixed; 
more seldom grape-juice, evaporated wine, and elder-berry extract 
areadded. ‘‘Strong, black,and sweet” form the criterion of excellence, 
according to the Portuguese government ; what we require at present 
is not this, but the exact chemical composition of unblended, unfor- 
tified vintage wines; until these are obtained we have no means of 
making true comparisons. 
For the detection of most of the adulterations of wine at home and 
abroad, there is but one scientific method possible, This may be 
summed up in these words,—accurate comparison with standard 
wines: by means of these we shall be able to trust to the science 
of the chemist, whilst without them we can only depend on the skill 
of the taster acquired by use. 
[H. B. Ji] 
WEEKLY EVENING MEETING, 
Friday, March 3. 
Grorcr Dopp, Esq., F.S.A., Vice-President, in the Chair. 
Rev. Bapen Powet, M.A., V.P.R.S., F.R.A.S., F.G.S., 
SAvILIAN ProressoR OF GEOMETRY, OXFORD. 
On certain Phenomena of Rotatory Motion. 
Tue mechanical principle of “ the composition of Rotatory Motion,” 
originally discovered by Frisi about 1750, (see Frisius de Rotatione, 
Op. ii. 134, 157, and Cosmographia, ii. 24) is equally simple in its 
nature, important and fertile in its consequences and applications,— 
and susceptible of the easiest explanation and experimental illustra- 
tion; yet it has been singularly lost sight of in the common elementary 
treatises. It is indeed discussed and applied in a Mathematical form 
in Mr. Airy’s Tract on Precession (Math. Tracts, p. 192, 2nd ed.) ; 
and the theorem is stated by Professor Playfair in his “ Outlines of 
Natural Philosophy” (i, 144), and its application explained (ib. ii. 
