SCIENTIFIC NOTES.

Press, Volume XVIII, Issue 2493, 27 April 1871, Page 3

SCIENTIFIC NOTES.

[Harper's MagazineJ] " A new mode of distinguishing death w has been recently submitted to the B< consideration of the Academy of Mcdi- ci ciue, Paris. It consists in the insertion of a bright steel needle into the body; and it is said that when life is present the needle soon becomes tar- . nished by oxidation ; while, on the n other hnnd, if death has taken place, c the needle will retain its brightness ?' for half-an-hour or more. According '' to Dr. Laborde, the author of the com- P raunication, oxidation, with its attendant electrical phenomena, indicates w that death is only apparent, and the v entire absence of oxidation is a sign of f. real death. " The great frequency of fires during v summer in the pine forests of Germany and France, under circumstances where ~ there was no suspicion of accidental or wilful incendiarism, has suggested w to Mr Schrader the idea that these £ may be in a measure spontaneous. In tl most of these forests the resin is col- o; lected in large quantities from punch tures made in the bark, and an exuda- . tion of the same substance may take w place whenever the bark is accidentally rs cracked. Mr Schrader suggests that n the tear-ehaped drops of resin, in run- J ning from the trees, may form lenses, J ( through which the rays of the eun may y

be concentrated, and act upon the inflammable surroundings, and thereby i sot fire to thorn. In many cases, possibly, a vapour of escaping turpentine tn:iy also, by its combustibility, causa (lie fire to spread with greater rapidity. It is stated, as the result of recenfe experiments, that pale yellow is to be preferred to all other colours for signal lights, as being the tint most quickly and readily recognised at a distance. Native sulphides of metal often, occur of much value in a metallurgical point of view, but which cannot be reduced, in consequence of the great scarcity of fuel. Dγ Kopp, in a recent paper, mentions the results of a series of experiments upon such substances, for the purpose of ascertaining whether certain chenp and abundant chemical re-ageuts can be made to act upon the minerals in question (without at the same time affecting their gangue), so as to bring them into a condition fit for beiug readily converted into metals. Tho re-agents . named as suitable for the purpose in question are common salt, chloride of iron, and hydrocholoric acid. In this paper it ia stated that the most economical method of extracting the small quantity of copper present in previously burned pyrites consists in first exposing the burned substance to heafc and moisture, and then pouring over the material a solution of common salt. A small addition of hydroeboloric acid is useful, and the cepper in this way becomes converted into a soluble chlorido. In former times secret correspondence was conducted by writing with milk, diluted with sulphuric acid, or a solution of cobalt, which, coloross under ordinary circumstances, becomes visible by heating the paper. At the present time, however, a very different class of fluids is used, especially the dilute salino solutions), which are known to the receiver of the letter alone. "Without being specially skilled in chemistry, the receiver needs only to know the particular solution in which the paper baa been moistened to have it in his power to bring the invisible characters to light. Thus, should the letter be written with a solution of of lead, one of sulphide of potassium will have the desired effect. Or, if nitrate of silver be used, tho paper must be dipped in a solution of ammonia. Iv either case a. black letter is the result. Any colorless solution, however, which, when mixed with another equally colorless, produces a colored deposit, may be amployed for this purpose. The number of substances, therefore, available is very great, in the many possible combinations of tho kind. The whole subject has recently received renewed ittention in Germany and England since the introduction of the " correspondence cardc," as it is hoped to 3ecure the privacy of an ordinary letter by writing upon them with sympathetic ink. Our readers will remember that the; German exploring expedition which' • went out in 1869 for the purpose of Arctic discovery has lately returned iiome, the sailing vessel of the expedition having been wrecked on the jast coast of Greenland, her entire ;rew, however, being saved. The iteamer returned in good condition. Enough of the results of the expedi;ion havo been published to furnish ,he means of judging, to some extent, >f the advantages secured, which ire thought to be of great infce•est; not the least being the acquisition »f a foothold of property •in the lorth, possession having been taken of i previously unoccupied portion of the ;oast of Greenland, extending forabout 10 German miles, or from lat. 75 deg. o lat. 77 deg. An apology is made or the absence of any considerable tinount of actual discovery, on account )f the excessive rigour of the winds, ;his being very much_greater than ;hat experienced in the neighbouring •egions during the previous explora:ions on the part of English vessels. Fhe portion of Greenland explored jy this expedition in characterised by a rery deep fiord, the head of which was not reached in a dietance over eighty miles; and it was thought to be not impossible that it extended all the way icross to the water on the opposite ■tide. The most interesting feature of the land, however, was the occurrence if extensive meadows, starred with lowers, with butterflies and bees playing about them, and having large herds grazing near by of reindeer and musk jxen. The lowest temperature experienced was about —58 deg. Fahr., ;his occurring on the 21st Feb., 1870. Fhe wind was found to be of extraorlinary severity, Robinson's anemometer ndicating a rate of velocity of sixtyjeven miles in tho hour, which, it was relieved, would render sledging parties mtirely impracticable. The auroral ight, to the surprise of the beholders, who expected to see it in the west or »outh-west, was actually in the southeast. Among the geological discoveries were beds of brown coal, and numerous ? ossil remains. Deep sea soundings were made, and collections taken Prom a depth of 1500 fathoms. One important conclusion arrived at by the expedition was that small vessels were mited for polar exploration, and that it would be madness to attempt, as is proposed by the French, the use of a thousand ton ship. Steamers, too, were believed to be the only form of vessels suited for research on the sastern coast of Greenland, anything like reachit-g the coast in a sailing vessel being entirely out of the question.