188. -°- Miscellanies. 
exists in » the eye; ‘in the posterior capsule of the lens ; aa: thus the — 
third i image is accounted for 
M. ‘Sanson, a distinguished French surgeon, has taken: advantage 
of the above facts, to distinguish cataract from amaurosis, and has 
been enabled _ to determine by this means some cases of supposed - 
amaurosis to be in fact cataract, and has treated them — J 
operation. 
Dr. Mackenzie, an eminent ophthalmologist of Glasgow, Gee also 
employed this means to determine the condition of the eye in glau- 
coma. Dr. Hays remarked that he had resorted to the catoptric 
examination of the eye in many cases, and believed that it would 
prove as valuable a means of diagnosis in some of the diseases of the 
eye, as auscultation is in those of the chest. 
Dr. Hays exhibited and explained several models, designed and con- 
structed by Dr. John Neill, resident surgeon at Wills’ Hospital, for the 
‘purpose of illustrating the catoptric phenomena just explained. 
Dr. Patterson communicated verbally a method of using thin sheets 
of Jead by the blind i in writing, reading, and musical notation, invented 
by Mr. Joseph Saxton. The sheets of lead are three thousandths of 
an inch in thickness. Dr. Patterson presented specimens of the wri- 
ting and musical notation. 
Dr. Bache communicated the decease of Mr. George Pollok, @ 
_. ~ member of the Society, who died in April last. 
: _ May 17, 1839.—Dr. Hare made the following verbal communica- 
tion relative to the blasting of rocks by the aid of galvanic ignition 
in firing the charge. 
The Doctor called the attention of the Society to the fact, that he 
ae had, so long ago as the summer of 1831, demonstrated the safety, 
certainty, and facility, which would arise in rock-blasting, whether 
under water or otherwise, from a resort to galvanic apparatus as the 
means of igniting the gunpowder employed. His efforts had been 
incited originally by those of a person named Shaw, who had pro 
cured a patent for employing mechanical electricity for the purpose} 
but who, finding that method of operating too precarious to be useful, 
had applied to Dr. Hare to acquire a knowledge of more eflectua 
means. This led to the experiments of which the result has been 
published, both in the newspapers, and in the Journal of the Frank- 
o lin Institute. The subject was now referred to, in consequence 
the recent publication of analogous experiments by his friend, Prof. 
: - Daniell, of King’s College, imines who, in the case in point, no 
i doubt as in that in which he had * reinvented” Dr. Hare’s concentric 
_blowpipe, was ignorant of the results previously obtained in this cout 
of. Daniell had, in blasting, used the highly ingenious app 
