SCIENTIFIC SUMMARY. 
381 
were not permanent, but sometimes went out, returning again when the snow 
was heaviest. This was from one to three a.m. At daylight I carefully ex- 
amined the place, but no discoloration of the paint was to be seen. The 
stem in this part is wood, and iron plates bolted on each side, and it appears 
to me that the jets came out between the wood and the iron. The barometer 
stood at 29 ‘1 in. The ship is an iron one, but I did not observe any altera- 
tion or other effect upon the compasses. I have seen the same phenomenon 
abroad, but never before in these latitudes.” 
MICROSCOPY. 
The Binocular ivith high Powers. — As we stated in our last, Messrs. Powell 
& Lealand have devised a prism apparatus, by means of which the binocu- 
lar ceases to be any longer a mere toy for exhibition at conversazioni. The 
instrument can now be easily used with the X V inch objective, and 
even with T V inch. Two contrivances have been already employed, — the 
one we have referred to, and that of Mr. Wenham. We do not think there is 
much material difference between the two arrange- 
ments as regards their powers of working. We have 
examined the circulation in Vallisneria with Messrs. 
Powell & Lealand’s apparatus, under the T V and 
No. 1 eye-piece, and have been much pleased with 
the result. Although the stereoscopic effect is by no 
means so great as one might have expected, there is 
considerable “ relief ” shown, as may be seen by 
watching the movements of the green corpuscles. 
Besides there is, of course, the advantage of employing both eyes, which, 
even if there were no stereoscopic effect, affords the observer considerable ease 
during prolonged investigation. The action of Messrs. Powell & Lealand’s 
device will be apparent from the accompanying diagram. 
New Cells for mounting Objects. — Mr. Charles Collins, of Titchfield Street, 
has just shown us some very ingenious cells, which bid fair to do away with 
the old glass forms. They are made of pure tin, and being cut by a punch 
made specially for the purpose, there is no trace of bevelling on their edges. 
From the difficulty in cutting out thin glass rings for cells, their price is 
necessarily very high ; the rings of tin can be sold at less than half the price of 
the glass ones, and may be more easily mounted. It suggested itself to us that 
the different expansions of glass and tin would cause cells so constructed to 
leak on exposure to changes of temperature ; but Mr. Collins assures us that 
this is not the case. 
The Wheels of Chirodita. — Messrs. Baker have sent us an admirable speci- 
men of the “ wheels ” of this aberrant and worm-like echinoderm. They are 
certainly the finest specimens we have yet seen, and since Messrs. Baker have 
2 d 2 
