A NEW ONE-SIXTH OBJECTIVE. 69 
appropriately so called. It does not fruit in Britain, and is often 
confounded with Z: Blandovii, a very rare Moss, and respecting 
which a very interesting correspondence took place between Wilson 
and Dr. Hooker. Found only on the Scottish mountains is 
Brachythecium reflecum, named from the reflexed margins of its 
leaves; while the curved capsule gives the specific name to 
LEurynchium circinatum, the curved Feather Moss. 
A very minute and rather rare species growing in dark green 
patches on moist shady rocks throughout Great Britain and on 
stones in Miller’s Dale, Derbyshire, is Eurynchium Teesdalit. 
Found on limestone rocks and stones, but not fruiting in Britain, 
is Rhynchostegium depressum, and on the sandy shore at Southport 
RR. megapolitanum. 
The beautiful and extremely common species, Plagiothectum 
Borrerianum, the elegant Feather Moss, grows in extensive shining 
green patches on shady banks and rocks, and is usually barren. 
Stems prostrate with complanate branches; leaves complanate, 
ovate-lanceolate, oblique, tapering to a slender serrulate point, 
nerveless or two-nerved at base ; margin plane capsule ovate, more 
or less pendulous ; lid conical, shortly rostellate ; dioicous. 
Amblystegium Sprucet, found at Teesdale and at Todmorden, is 
rare on shady sub-alpine rocks, and on wet alpine rocks is Hypnum 
sarmentosum, the twig Feather Moss. 
A NEW ONE-SIXTH OBJECTIVE. 
By A. Y. Moore, M.D. 
FEW months ago the Spencers constructed a homogeneous 
immersion ;); inch objective of 125° balsam angle, which was 
the best they had ever made, and it certainly was a lens deserving 
of praise. 
Some time after the completion of the formula of this 7'5, they 
were requested by me to make a new homogeneous ? in., in which 
resolving power should be held paramount, and which should 
excel both the new 54, and their + of 120°b.a. The new ¢ 
would, of course, necessitate a new formula, and that of the > 
was modified and adapted to the power of the %. 
The Spencers assured me that this + was positively the best 
objective they had ever looked through, and as a few words con- 
cerning it may be of interest I will describe it. 
The mounting is similar to that of the old }, of red brass and 
gracefully proportioned. By means of a graduated screw collar 
a rectilinear motion is given to the back systems sufficient to 
