SCIENTIFIC SUMMARY. 
213 
montli, lie had succeeded in distinguishing the form of a solar prominence. 
A spectroscope was used ; a narrow slit was inserted after the train of 
prisms before the object-glass of the little telescope. This slit limited the 
light entering the telescope to that of the refrangibility of the bright line 
coincident with c. The slit of the spectroscope was then widened sufE- 
ciently to admit the form of the prominence to be seen. The spectrum 
then became so impure that the prominence could not then be discerned. 
A great part of the light of refrangibilities removed far from that of c was 
then absorbed by a piece of deep ruby glass. The prominence was then 
distinctly perceived. 
Metals in the Galvanic Current. — The Chemical News (January 1) describes 
the following experiment, which has recently been made by Herr Wohler, 
and which is supplementary to others of a similar kind: — Palladium as 
positive electrode of two Bunsen’s cells, immersed in acidulated (sulph. 
acid) water, becomes gradually covered with an almost black film of 
peroxide (PdOj). Upon lead and thalium brown peroxide and black oxide 
are deposited. Osmium, in the ordinary porous condition, is freely converted 
into osmic acid (OsOJ. If, as electrolyte, a dilute solution of sodium 
hydrate is employed, the solution assumes a deep yellow colour, while on 
the negative electrode metal is deposited. The same is the case with 
ruthenium. Osm-iridium, in its natural state, readily dissolves in the 
alkaline electrolyte. 
Hmu to Take Oleographs . — Dr. P. C. Moffat has given the following 
account of a method of producing these interesting results: — The oil 
patterns* uninjured can as readily be transferred from the surface of the 
water, and permanently fixed to be placed in our albums, as we can pour 
water from one vessel to another. No matter what colours we desire, we 
can obtain them of any hue we please. They rival the most beautiful 
photographs. The faintest tracery is brought out with the most perfect 
fidelity. Two well-known photographers, to whom they were shown, 
declared they were excellent photographs, and yet not a trace of the 
chemicals photographers use was employed. The process can be described 
in three lines : — Obtain the oil pattern, note the time, lay a piece of glazed 
surface paper on the pattern for an instant, take it off, place on the surface 
of a plate of ink for a moment, remove and wash oft' the excess of ink with 
water, and your pattern is there as it was on the water. You now have an 
exquisite representation in black, as fine as any photograph. A scarlet is 
obtained by employing a solution of cochineal or any of the scarlet coal-tar 
colours. We have them in orange, red, scarlet, black, blue, and other tints. 
A good result is got by first passing the paper containing the pattern of oil 
through ink and then through cochineal. The principle of the matter is 
this. The paper absorbs the oil at several parts to the exclusion of the 
water. The ink colours the water parts, but at the; same time tints the oil parts 
very faintly, which gives it the appearance of relievo. Any kind of paper 
almost will do. Tissue, green, glazed, white, t&c. give pretty good results. 
Glass for Lenses. — It is stated that glass having a density of 4-4 is now 
manufactured by Messrs. Chance, the great Birmingham firm. 
Use of J^elegraphy in Ascertaining Longitude. — M. Quetelet has recently 
laid before the Belgian Academy of Sciences an account of the observations 
