52 
Lev. xi. 30, probably the Pterodactyle gecko, or " fan-foot," common in 
Egypt, but widely distributed. The Chameleon of the same passage he 
thought was the Monitor Niloticus, and the snail the true Chameleon 
Africanus, found in Syria and Egypt. The snail " which melteth," Fsl. 
lviii. 8, he thought referred to a slug which gradually consumed its sub- 
stance as it crawled, and left its slime behind. He said that he was glad 
to have the opportunity of calling attention to the fine collection of reptiles 
in the museum of the Institution, which so well illustrated his paper ; and 
said he hoped that they would be often made available for similar purposes- 
CHEMICAL AND PHOTOGRAPHIC SECTION. 
Wednesday, May 16 (postponed from May 9th). — The section ad- 
journed to the meeting of the Microscopical Society, in order to hear an 
address from Mr. H. C. Sorby, F.R.S., on his researches with the Micro- 
spectroscope. Mr. C. T. Hudson, M.A., LL.D., President of the 
Microscopical Society, occupied the chair. Mr. Sorby characterised the in- 
vestigations of the absorption bands produced in the spectrum by various 
coloured solutions, as a more refined mode of recognising substances by 
their color, and described at some length the construction of the ' direct- 
vision' spectroscope now applied to the microscope, the arrangements for 
comparing two spectra together simultaneously by an ingenious arrange- 
ment of reflecting prisms, and his mode of examining the spectra of 
coloured solutions, crystals, and other substances. He dwelt upon the spectra 
of blood, fresh, old, and when submitted to the action of various chemi- 
cal reagents, pointing out that no other red colouring matter with which 
he was acquainted — and he had examined all he could think of— behaved 
in this way, so that the test was very reliable, as well as delicate, T ^th 
grain being detected with perfect ease, and even i-^Voth grain with care. 
The testing of cloth and various fabrics for blood stains was comparatively 
easy, but in examining stains on leather, the tannic acid interfered to some 
extent. Mr. Sorby then mentioned several curious facts that he had made 
out in the course of his investigations. The same substance frequently 
gave a different spectrum when in the solid state and in solution, and even 
then the position of the bands often varied with the solvent. Different 
salts of the same metal sometimes gave different spectra, as in the case of 
nitrate and acetate of uranium. Alum in solution had a remarkable effect 
in intensifying the colouring power and action on the spectrum, of many 
substances. The act of solution upon a double salt produced an effect 
from which it was inferred, on optical grounds only, that the salt was 
decomposed. Mr. Sorby exhibited a small micro-spectroscope, which dis- 
played several spectra very beautifully, and which was very easy of mani- 
pulation ; and Dr. W. 13. Ilerapath showed Mr. Browning's eye-piece 
direct-vision spectrosoope, adapted to his large instrument. 
