1819.) Royal Society. 307 
upon the angle which the incident ray forms with the axis of the 
crystal. The paper contained numerous experimental details. 
At this meeting there was also read a paper, by Sir E. Home, 
giving an account of the fossil skeleton of an animal, several 
parts of which have been already laid before the Society in three 
separate papers. The author, after referring to his former papers, 
proceeded to describe, in general terms, and principally with the 
view of correcting his previous account, a specimen recently 
found nearly in an entire state. The only parts wanting were some 
of the bones of the pelvis and the lower part of the sternum. A 
beautiful drawing of the animal of its natural size accompanied 
the paper, which rendered minute description unnecessary. 
March ii.—-A paper, by C. Bonnycastle, Esq. was read, 
entitled, “‘On the Pressures which sustain a heavy Body in 
Equilibrium when the Points of Support are more tian three.” 
The author, after some general remarks, observed, that this is a 
problem which has hitherto never been satisfactorily investigated, 
though its assistauce is necessary in estimating the strength of 
bridges and materials in general, and in determining the deflec- 
tion and curvature of elastic plates. The difficulties attending 
‘the investigation of this problem were referred by Mr. B. to the 
too great generality of the method of investigation hitherto 
employed, and which, for the most part, has consisted not in 
the direct solution of the equation, but in comparing it with 
another admitting of a more easy solution. The author, after 
some further remarks, observed, that there is no method purely 
mathematical by which the difficulty can be surmounted; and 
that when abstractedly considered it appears impossible to deter- 
mine the pressures which a heavy body exerts when supported 
on four or more fulcra. By considering, however, the cir- 
cumstances under which pressure is usually generated, we shall 
be enabled, the author continued, to discover the law of its dis- 
tribution, and this law must always govern its proportional quan- 
tities and intensities. ‘Mr. B. then proceeded to examine the 
subject in this point of view, and to explain the general law of 
the distribution of pressure on determinate fulcra in different 
instances, The paper concluded with an investigation of the 
case, when the number of points of support is infinite; or in 
other words, consists of a line or plane surface. 
March 18,—A letter by Dr. Granville was read, the object 
of which was to correct a mistake in his paper in the last 
volume of the Transactions of the Royal Society, and which had 
been pointed out to him by Dr. Maton. 
SOCIETY FOR THE ENCOURAGEMENT OF ARTS, MANUFAC- 
TURES, AND COMMERCE. 
5 This Society has voted the following rewards since February 
ast: 
Mr. Barraud’s Double Violincello.—This instrument possesses 
1 ae 
