29 
fetched nearly £400 per ton, and the colouring matter, called Litmus, 
could be obtained from any Lichen which yielded Orchil. Iceland moss 
contained a nutritious, starchy mucilage. Various species were used by 
the Canadian hunters as a diet, under the name of Tripe de Roche ; but if 
long used as food it occasioned diarrhoaa. The reindeer moss, which was 
so valuable tothe Laplanders, was abundant on our moors. Besides these 
uses of Lichens, one lichen might be named which occasionally appeared 
in enormous quantities in Persia and Tartary, and was eagerly eaten by 
the natives who imagined that, like the manna of the Israelites, it had 
fajlen from heaven. At times it had been known to cover the ground 
to the depth of five or six inches. 
The Paper was illustrated by admirable drawings and specimens. 
Mr. H. Goss exhibited several British moths whose larvz fed on 
different species of Lichens, which they resembled in colour and 
markings. 
Mr. T. Henwnaz exhibited and presented photographs of parallel 
cylindrical glass rods, rotated over similar rods, to illustrate the effects 
of illumination. The results were very curious, some exactly re- 
sembling the hemispherical markings ascribed to some diatoms and 
the note of admiration marks on the Podura scale. 
FEBRUARY 23RD. 
MICROSCOPICAL MEETING. 
Mr. Henwnau, alluding to the photographs presented by him at 
the last meeting, of cylindrical rods rotated over each other, remarked 
that they were intended to show how careful we must be in referring 
‘markings to objects themselves, and not to the method of illumination 
employed in microscopical investigation, as he believed was the case 
with some of the ‘‘ spectral” dots seen and described by Dr. Piggott, 
Mr. Wonror exhibited Beck’s illusive photographs of a small 
tumbler partly covered with hemispheres, and which appeared, accord- 
ing to the way in which the light fell on them, either hemispherical 
elevations or hexagonal depressions. In illustration of Mr. Hennah’s 
