166 : JMiscellanies. 
the weight the blade gives, till the object is attained. If the ragor 
have been properly ground and prepared, a very fine edge will be 
given in a few seconds, and it may be renewed again during a very 
long period, wholly by the same means. 
The author has had a razor in constant use during more than two 
years and a half, and no visible portion of its metal has been wom 
away, though the edge has remained as fine as possible, and he has. 
never at any one time spent a quarter of a minute in setting it. He 
thinks it operates best when the temperature of the blade has been 
raised by the aid of warm water. 
Although a cylindrical bar is much superior to a plane surface for 
for giving an edge to a razor or pen knife, it is ill calculated to give a 
fine point to a lancet. For this purpose a plane surface is madea 
quarter of an inch wide on one side of the bar, and this form is found 
to be extensively useful. 
The author finds that the material which appeared to receive the 
most eager edge (and very durable) was wootz, and that which re 
ceived the smoothest edge and best adapted to surgical purposes, ¥2% 
a mixture of rhodium and steel; the powers of pure steel appe 
to be intermediate.—Journal of the Royal Institution, Vol. I, p- !*: 
3. Interesting optical experiments.—If, without closing the lids 
the left eye be covered with the hand, or some other obstacle, and @ 
candle or lamp be held in the right hand within two or three inches 
of the right eye but rather below it, (keeping the eye directed straight 
forward,) on moving the candle slowly backward and forward, ine 
from right to left, (or if the candle be held on the right side of the 
eye it may be moved up and down,) a spectrum appears after a short 
time in which the blood vessels of the retina, with all their ramilic 
tions, are distinctly seen projected, as it were, on a plane without te 
eye, and greatly magnified. They seem to proceed from the opt’ 
nerve, and consist of two upper and two lower principal branches 
which are variously ramified towards the field of vision, where a dark 
point is seen, which sometimes appears concave. A similar but 
verted figure, and less distinct, appears in the left eye. ‘The 08! 
of the vessels is a dark oval spot, with a light areola; the figure 
self, or rather fragments of it, are seen under various other circull 
stances. ‘There can be no doubt that it is formed by the central ves 
sels of the retina, A remarkable circumstance of this phenomen® 
is, that at the point corresponding to the projection of the forame 
