NORTH OF ENGLAND MICROSCOPICAL SOCIETY. 19 
glass in my collection which is very fair on Podura when the screw 
collar is in one position, and also is a good diatom resolver with 
its collar in another position; but when all its zones are tried at 
once, by the direct illumination, it utterly breaks down. 
With regard to A. pellucida, the strongest resolution is obtained 
with P. and L’s vertical illuminator. The long striz can only be 
seen by this method. Spurious long. strize may be easily seen ; but 
the true lines are very difficult, and may be estimated to be 120,000 
to the inch at the lowest. The transverse I have counted 
repeatedly, and find them, in Van Heurck’s specimens, very constant 
at 95,000 per inch. The best picture of the trans-strize is obtained 
with oil imm. j, N.A. 1°43, or oil imm. 4 N.A. 1°38, and P. and 
L.’s oil immersion condenser, wsed dry, with single slot, edge 
of flame direct, valve being dry on cover. The lowest angled glass, 
with which I have seen the trans-strie, is a water imm, 4 N.A. 
1‘08, and the lowest power 4%, N.A. 1°17. 
NORTH OF ENGLAND MICROSCOPICAL 
SOCIETY. 
'HE last monthly meeting of this Society was held on the even- 
ing of Tuesday, the 4th inst., in the patent room of the Literary 
and Philosophical Society, Newcastle-upon-Tyne ; the President, 
Mason Watson, Esq., occupied the chair. The Rev. W. Johnson, 
of Hartlepool, sent a description with illustrative slides and draw- 
ings of a Lichen found in Cumberland, and new to Great Britain ; 
an abstract of which is appended :— 
“* Strostphon saxicola (Nag) is a small byssaceous lichen found 
growing on damp rocks near to Ennerdale Lake, Cumberland, 1881. 
It is black when dry, and thinly scattered on the rock ina dark 
crust. The filaments are very minute, entangled and depressed ; 
when magnified they are seen to be variously branched and some- 
what mammillose. The cellules are in single series, doubling in 
the older filaments, clearly defined, and roundish in the young 
branches ; the vagina is fuscous and narrow ; fruit not seen.” 
The Hon. Sec., Mr. M. H. Robson, read a short paper, noting 
the detection of Alcyonella stagnorum, Nitalla (probably) flexzlis, 
and Cystopteris dentata, new to this district, and enumerated a list 
of other objects, for which new habitats may be claimed. 
Mr. John S. B. Bell, C.E., gave a description of a new form of 
Warm Stage, and adaptation of hemispherical lens for resolution of 
Diatoms ; an apparatus for maintaining the slide at any temperature 
