SCIENTIFIC SUMMARY. 
325 
■cully on the presence of undoubted Silurian and Carboniferous fossils at the 
highest latitude yet reached, namely 82° 45' north. 
Stromatopora and Loftusia. — Principal Dawson has contributed a state- 
ment of his views as to the nature of those problematical fossils from the 
Palaeozoic rocks which are commonly known as Stromatopora. They are 
massive fossils, often showing concentric structures when weathered, and 
have been referred by different writers to the Sponges, to the Corals, to the 
Hydroida as allied to Hy dr actinia, and to the Foraminifera. Principal 
Dawson says that Stromatopora is “ a calcareous, non-spicular body, com- 
posed of continuous concentric porous laminae, thickened with supplemental 
deposit, and connected by vertical pillars, most of which are solid ; ” and he 
maintains his old opinion that Stromatopora is a Foraminiferal organism and 
the Palaeozoic representative of the Laurentian Eozoon. 
Dr. G. M. Dawson has made the interesting discovery of a species of 
Loftusia in a Limestone, probably of Carboniferous age, which occurs in 
British Columbia in the banks of Marble Canon, Frazer River. He names 
this species Loftusia Columbiana. As the genus Loftusia was established for 
the reception of a tertiary Persian fossil Foraminifer, this discovery is of 
.great interest provided the reference of the North American form to this 
genus be confirmed. Loftusia Columbiana is much smaller than L. persica 
(0*3 inch long) ; it occurs here and there in patches in the limestone, but the 
number of specimens when it does appear is very great. — ( Proc . Geol. Soc., 
June 5, 1878.) 
MICROSCOPY. 
The New Oil-immersion Object-glass. — The Rev. W. H. Dallinger writes to 
Nature ” : — “ As a piece of workmanship this lens is extremely fine 5 and 
it can be used with quite as much ease as an ordinary immersion quarter- 
inch objective. It works admirably with Powell and Lealand’s ordinary 
sub-stage condenser, with Wenham’s reflex illuminator, and with the small 
plano-convex lens which the maker sends with it to be fastened to the under 
surface of the slide with the oil of cedar wood. But I have also secured 
admirable results with the illuminating lens of Powell and Lealand’s sup- 
plementary stage, which gives entire command over the angle of the illumi- 
mating ray. 
“ The spherical aberration is beautifully corrected, the field being per- 
fectly flat. The colour corrections are, so far the lens goes, equally perfect ; 
but are somewhat conditioned by the dispersive power of the oil, which can 
be modified readily. The sharpness and brilliance of the definition which 
this lens yields are absolutely unsurpassed, in my experience ; and it has a 
very great power of penetration. 
“ I tested it with a series of tests with which I have proved and com- 
pared the glasses of various makers in England, the Continent, and America, 
for some years. Up to the time of receiving this lens, the £-inch that had 
• done the most in my hands was one of the ‘ new formula ’ lenses of Powell 
and Lealand. It is but justice to say that all my most crucial tests were 
equally mastered by the lens of Zeiss. I have not been able to do more 
with it than with the English glass, but the same results can be accom- 
