274 Proceedings of the Royal Society. 
heating potassium with dry fluosilicate of potassa, by which a sili- 
curet of potassium and fluate of potassa are formed; and 
which, when thoroughly washed with water, leaves a residue of 
hydroguret of silicium. It burns imperfectly in air and oxygen, 
at a red heat; is of a brown colour, and is acted upon by no acid 
except the fluoric. Silicium is readily oxydized when heated 
with carbonate of potassa or of soda, 100 parts producing 208 
of silica. It burns in the vapour of sulphur, producing a white 
substance, which yields sulphuretted hydrogen when thrown into 
water, and silica remains in solution. In chlorine silicium burns 
at a red heat, and yields a colourless liquid chloride, the odour of 
which resembles that of cyanogen. In its nascent state silicium 
appears to combine with the metals. 
This letter concludes with some remarks upon zirconium, ob- 
tained by the action of potassium on the alkaline fluate of zir- 
conia; it is black, feebly acted upon by nitro-muriatic acid, so- 
luble in sulphuric acid, and readily so in fluoric, with the disen- 
gagement of hydrogen. It unites with sulphur and chlorine, and 
readily burns in the air at a heat below redness, 
Thanks ordered, 
Thursday, May 27. 
A paper by Dr. Wollaston was read, — 
On the apparent Direction of the Eyes in a Portrait. 
Our account of this paper must necessarily be very imperfect, 
for want of the very curious and interesting drawings which ac- 
companied it. Dr. W. observed that when we consider the pre- 
cision with which we commonly judge whether the eyes of another 
person are fixed upon ourselves, it is surprising that the grounds 
of such judgment are not distinctly known, and that most per- 
sons in attempting to explain the subject would overlook some of 
the circumstances by which they are generally guided. Though it 
may not be possible to demonstrate by any decisive experiment on 
the eyes of living persons what those circumstances are, we may 
find convincing arguments to prove their influence, if it can be 
shewn, in the case of portraits, that the same ready decision that 
