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When Professor Bell ascertained that ir ?was possible to produce figures on the retina which might be examined after the death of ibe animal, some discussion task place ia fccitutitic circles as to whether this fact might be made use of in affording direct eviderce in cafes of murder. Dr. \V. C. Ayiee, who has experimented extensively on this subject, in an article iu

the Hew 'York Medical Journal answers tliis question in the negative. He says that while he was working in the laboratory of Professor liiihue, at Heidelberg, where he has been conducting his experiments, the professor proposed that he sh.ou.ld make a picture of Helmhohz and send it to the latter as an acknowledgment of. the value of his researchee in physiological optics. Dr. Ajres, therefore, provided himself with a large negative or' S.elm holtz and set about making an opto gram from it, according to the moat ap proved methods. The negative was placed over the eye, which had been dosed with atropire. The animal was in the dark room for hours. The sun was shining brightly, eo that there was the best of light ; ana every precaution having been taken the retina was exposed for four minutes. There was a dull picture on the cornea, and when the retina was examined there was found en image of lielmhoVtz's shirt collar and of the end of his nose. The light was not bright enough, or rather there was not enough transmitted through the negative to bleach tbe visual purple. As there is always an active rhodogenesis in the living retina, and it might have been strong-enough in this cate to rettore the visual purple as fust te it was bleached, Dr. Ayres cut off the head of a rabbit and waited until all such power on the part of the retina was certainly done away with, and then repeated the experiment. The result was a little better than the preceding', but the optogram was by no meanseuliiciently distinct for one to lecognise even that it was intended for a picture. Dr. Ayres, therefore, came to tlit conclusion tint euch an optogrntn was in: possible and gave up tbe plau. Since this experiment failed so signally, he believes it utterly idle to look for the picture of a man's face, or of the surroundings, on the jttis:a of a person who has met a Fudden death, even under the in jst f ivor- sble circumstances. In further research Dr. LeBon has found that collidiue, the new alk&ioii which he bus discovered to exist in tobacco smoke, ih a liquid of agreeable aiid very penetrating odor, -and us poibun jua as , nicotine, tat

twentieth of one drop sufficing to kill ft frog. The headache, giddiness, and nausea which are produced when certain tobac cos, euch as those of Havana and the Levant, that contain little nicotine, are smoked, are due to the presence of this and other aromatic principles and of prus3ic acid, and it is because of the absence of these that no such effects result from the nee of Eome tobaccos that are rich in nicotine. The dark semi-liquid matter -which condenses in pipes and cigar holders contains both collidine and nicotine, with prussic acid, carbonate of ammonia, tar, and other c impounds. It is very poisonous ; two or three drops of it will kill a small animal. The com bustion of tobacco destroys but a small part of the nicotine, and most of this appears in the smoke. The proportion absorbed by smokers varies according to circumstances, but hardly ever falls below 50 centi grammes per 100 grammes of tobacco burnt. About the same quantity of am monia is absorbed at the sime time. Naturally more of the poisonous principles are absorbed where the smoke is breathed (as in a room ) ; less in the open air. A frog placed in a receiver containing a solu tion of nicotine, with about one drop of that substance to a littla water, succumbs in a few hours. Tobacco smoke contains about 8 milliters of carbonic oxide per 103 grfimmes of tobacco burnt. The poisonous properties of tobacco smoke are not due to this gas, as has been maintained in Ger many. French newspapers report the dissovery in Algiers, by the arcL:ejlogist II. Tarry, of a city which had been entombed in the sand. M. TaTry's attention had been awakened by the mound-like appearance of the sandy soil, and some digging brought to light the minarets and upper portion of a mosque. Further excavations laid bare a terrace, a tower, and about a dozen house?, all in excellent preservation. He reported his discovery to the Government of Algiers, which has undertaken to have tho site thoroughly explored. The place ia in the southern part of the province, not far from the town of Ouargla, and exposed to the full blast of the sandy winds from the desert. Probably a succession of siroccos bearing clouds of sand completely filled up tbe 6U eel* and houses, making-the town uninhabitable, and so drove out the popula tion. At present there is no ground for conjecture as to tJie date of the occurrence. In devising a system for the thorough disinfection of vessels on board of which cases of smallpox had occurred, the Austrian Government, through its mcdicil experte, retorted to the following method : — Sulphur to the extent of twelve grains per cubic meter of tbe space to be disin fected was first burned in an earthen ware vessel or bu^in, placed in the centre of a mats of sand to prevent all risk of fire : every article of clothing, ail tbe linen, &-., were hung scrore the cabin, the latter being then hermetically closed for three hours, and afterwards exposed to the strongest possible draughts nr wr for twelve hours ; iiui'.lly, the wall?, floor, ceiling, &c, were washed with one kilogramme of lime, or one-half a kilogramme of chloride of zinc, to eveiy hundred liteTs of water. During the last few months some corres pondence I has gone on in scientific journals with regard to the Reese circular saw. This saw, as many of our readera are aware, consists of a circular saiooth edged iron plate 42 inches in diameter and 2 irclies thick, which when revolved at a gic-at rate will divide — it is eaid without touching ic — a bar of steel placed in oppo-' gition to it and revolving in tbe opposite direction. It seems that the French press questioned tbe statements concerning I this apparatus which had appeared iu the Euglith and Americau papers, and accord ingly Air. Jacob Keese, the inventar of tbe saw, wrote to L-i Nature, dssc/ibiag the ' action of the saw, and giving an explana tion or, at all events, an attempted explana tion of the curious phenomena wbiih attend it» Accounts of this wonderful and seem ingly paradoxical mnchiiw have appeared in our columns at different times, and it will Ie remenjbered tbat when the steel baT3 revolving mtheraie oi '2'vX- revolutions per minute, is brought near the iron disk, to which a velocity of 2,300 revolutions | per minute, representing a tan^entical ! velocity of 25,260 feet, is given, the '?

The storage of electric force is the sub ject of tbe tollowiog letter, taken from tbe Ixradon Times ef Hay 16 : — Permit me, through the Times, to record the accomplishment of a fact unparalleled in the annals of modern science. A short time ago your able Paris eoirespoodtnt announced tbe diacovery by M. Gasille Faure of Tbe practical means of storing electric energy and rendering it portable, so aa to be applied to many purges hitherto con sideied. if not impjuible, extremely difficult. Ibe publio seance at the tfociere d'Eooourage meut pcur l'Xndustrie, wbicb was presided over by the doitn of the French Academy of Science, M. J. U. Dumas, and at which were pretEDteoxne of our eminent English scientists, proved tLat M Fsures discovery was no mere laboratory experiment, bnt substantially one of gitat practical utility. I vraa myself ons of tbe many fceptioa, and would not on mere hearsby believe euoh uutenientt ai were being publicised in tbe Paris pre*e. Bat conviction came by puvonal veriooation, and thecrawn - it'g print of all has just been attained. It is ttiia I with tit record On Monday last, iu Paris, a Faure batter-, or r-ie sccoiuUire, we* cLatf:td witb tiie tiUcinc fl-ud direccfrom tbe ordinary Gjovc better}, aud ia my presence. It rc»j fce n.tre ecusumisally done from a Oran-u.t- or OM-uietin ?njmnine. Toe reoeptao'.e ocDfcieteri of lour Fju-« batteries, eaoh about S iu. oUuitter »o-l 10 (a. high, forming a 0)l-odnc») It-acen vr»*«l, »na containing aitttiikU: tlittle ot o.«:l«Uic I«ad aud siuti-js '. : .....

bar immediately rut-Its and a stream \ of molten metal of dazzling white- j ness escapes. Wonderful to say, | the temperature of the fu=ed matal \ is about the same as that of the surround- ! ing air, and the hind imy be placed in the glowing current -without auy injury belnr* sustained. The metal will not evea char j paper. When tkic fusion is going oa s ime j sparks fly off, aud it is fonad that when ? these have passed through the atmosphere \ for tome feet they become rapidly kented, and reach tbe temperature of iron which after beirg fused iu tbe ordinary oia-jner is allowtd to become solid again. Tiie melt irg f?oe8 on until th« b^r has been severed, ami it is then found tbat the vdpr s ».f tha cut are perfectly s-.nooth. ilr. Utei* sratf s that he was lei t'» cio fctiuct trie fusion saw by ;i wish to make a practical deiuorstratiua of Professor Tyndall's hypothetis tbat ' temperature is the meuiure of molecular velocity, as ? gravity is tha meaMire of matter.' His j exiilanation of the phenomenon is that tne I saw revolving at a great velocity makes ! molecules of air impinge on the bir j at a velocity of ~2o,'2iJU feet per minute, | aiid tbat thus the molecules of tbe bir are brought to the velocity of fusion, and the metal bpj:iris to melt. This explanation j appea) ^ t« be faulty, for if tbe molecules of j a body which is melted in tbe orJiu.ary way by heat move at a great velocity, tho xatuxal deduction would bd that, tice'centi, if lie molecules of the bodv are irivfin this

velocity beat should result as well as fusion. The English paper. Enjhicerinij, took exception to tbe explanation, and denied the accuracy of Mr. Reese's state ments with regard to tbis remarkable phtuorDeuon, affirming that it bad been louud by trial of one of the saws sold by Mr. lieete that tbe bar was not affected j unless it was placed iu contact with the j disk, aud tbat it was cut in a very rough, i tcauiier, a burr being made around 'the cir- j cumlrteuce of tbe bar, radial lines on the j cut face, while a broken tongue of ? metal with uLarp edgus was left | projtciir-g from the centre. Iu answer i to the article in Engineering, Air. Reese wrote reasserting the truth of his state ments, and offering to stand public trial of i the machine. He also wrote to the j Sdetitific American, in which journal tbe article from Engineering had been reprinted, in defence of hie theory, but in enlarging ou it he displayed such confused notions on the science of heat that it may be doubted whether his opinion is worthy of considera tion at all. The matter is still under dis cussion, and it would certainly be worth the while of eome scientist to investigate the phenomenon — if it exists — and pro nounce ae to tbe correctness of Mr. Reese's statements and theory.

wrapped in felt and rolled into a tpiral, wetted with acidulated water, and the whole placed in a square wooden hoi, meanuing about ons cublo foot and -weighing some 78 1b. Tnu waa pro tected by % loose wooden cover, through whiah tbe electrodes (in lead) protruded, and were flattened down for convenience ot transport. This box of ** electric energy' was handed to me by M. Faure, at my request, with the object ol submitting it for examination and measurement to our eminent electrician, Bir William Tnom cod, F.E.8., at the University of Gla«giw. I had the box by me all torough the journey from Paris on Tnecday night, including a five hours' delay at Calais. I arrived at Oharing Gross at 11 a.m. on Wednesday, after running the gauat let of Customs and police authorities, who suv picionaly looked askance, and seemed to doubt my statement that my box only held ' condensed lightning,' and contained na infernal machine or new explosive destined to illustrate some diabolical socialistic tragedy. From time to tune on the journey I tested the force of the discharge, and round it to have well maintained ita energy. From London to Glasgow required only another 10 ruufs, and finally, in about 73 boors from the time of ohBrgiDg in Pari*, I had the sstisfaotion of prefect mg to Sir William Thomson M. Faure's rare offering of a 'box of electrioity,' intact and potent, holding by measurement within that email space ol ooe cubic iojt a power equivalent to nearly one million of foi-t posne't! This woooerlul box is now de posited in tbe labnraiurj- oV the Glasjow Uui versity under the -vigilant eye of its director, and being submitted to a series of tests auJ measurements, tbe results of some of which made Sir William exclaim, «' Why, it's a lit tie witch.' I must hoc, however, trespass ou Sir Wil'iam'B ground as to the scientific re sults, wbich doubtless be himself will give to the public through the proper channels. Bat I mn£t generally say tbat the advantages to science and humanity at large which this dis covtry (or rather perficnoa ot Mr. G. Fiance's discovery) ia destised to afford are of saoh transcentient importance tbat we cannot {or the present form any correct estimate of their magnitude. Io t-hort, I have only to add tbat its future *fenis as certain at its stored force U potential and as brilliant as its own bright iipbt. Hut whatever may be the praotioal re* eult* obtained, 1 nave tbe *ati»faotion of reoord ing that for the fir»t time to my knowledge io the history cf ilie universe has a box of electric energy nearly equivalent Co a million oC poniiOe, contained within less than a cubic foit. of space, intact ai-d potential, been transported from France cr elsewhere to Great Britain.