In 1836, Mr. Andrew J. Crosse, while conducting some experiments in the formaiion of artificial crystals, discovered in a caustic solution a large number of insects of the aca/rus tribe;—mit't:'—t ae announcement of which made a considerable senatiuii in th'o aeientific world. These mites, since called the Cross,! mites," were never claimed by Mr. Crosse to have been sDontaneoualy generated, although he was charged with impioualy trying to imitate creative power. He bdieved the insects to have originated from germs conveyed by some unknown means into the solution. He repeatpd the experiment, and his own account of this discovery taken from a magazine of that day, together with an engraving of the simple apparatus he employed, we now present to our readers. He says : ' In the coarse of my endeavors to form artificial minerals by a long continued electric action on fluids holding in solii-tion such substances as were necessary to my purpose, I had iecourse to every variety of contrivance which I could think of so that, on the one hand, I might be enabled to keep up a ncver-i'aiiing electrical current of greater or less intensity or quality, or both, as the case seemed to require; and, on the other liand, tlrat the solutions made use of should be exposed t0 the eh.;ctxic action in the manner best calculated to effect the object in view. Amongst other contrivances, I constructed a wooden frame, of about two feet in hight, consisting of fear legs proceeding from a slielf at the bottom, supporting another at the top, containing a third in the middle. (Seen in section in Fig. 1) Each of theso shelves was about seven inches squan.l. The upper one was pierced with an aperture in which was fixed a funnel of Wedgwood ware, within which rested a quart basin on a circular piece of mahogany placed within the funnel. When this basin was filled with a fluid, a strip of flannel wetted with the same, was suspended over tlie edge of the basin and inside the funnel, which, acting as a siplion, conveyed the fluid out of the basin through the funnel in successivedrops. The middle shelf of the frame was likewise pierced with an aperture, in which was fixed a smaller fimnel of glass, which supported a piece of somewhat porous red oxide of iron from Vesuvius, immediately under the dropping of the upper funnel. This stone was kept con-oonstantly electrified by means of two platina wires on either Side of it, connected with the poles of a volatic battery of ninete3n pairs of S-inch zinc and copper single plates, in two porCelaia troughs, the cells of which were filled at first with water and 1-500th part of hydrochloric acid, but afterwards with water alone. I may ho re state that in all my subse-que,nt experiments relative to these insects, I filled the cells of the batteries employed with nothing but common water. The lower shelf merely supported a wide-mouthed bottle to receive the drops as they tell from 'ihe second funnel. When the bi;sin above w,is nearly emptied, the fluid was poured back again from the bottle below into the basin above, without disturbin,g the position of the stone. It was by mere chance that 1 selected this volcanic substance, choosing it from its partial porosity; nor do I believe that it had the slightest eff)ct in the production of the insects to be described. The fluid with which I filled the basin was made as follows: I reduced a piece of bhack flint to powder, having first exposed it to a red hea,t, and quenched it in water to make it friable. Of this piwder 1 took two ounces and mixed it intensely with six ouiices of carbol] ate of potassa, exposed it to a strong heat for fiiteon minutes in a blackload crucible in an air furnace, and then poured the fused compound on an iron plate, reduced it to powder while still warm, poured boiling water on it, and kept it boiling for some minutes in a sand bath. The greater part of the soluble glass thus fused was taken up by the. water, together with a portion of alumina from the crucible. I should have used one of silver, but none sufH-ciently large. To a portion of the silkai.e of potassa thus fused, I added some boiling water to dilute it, and tlwn slowly added hydrochloric acid to supersaturation. " ' A stirange remark was made on this part of the experiment at the meeting of the British Association at Liverpool, it being then gravely stated that it was impossible to add an add to a silicate of potassa without precipitating the silica ! This of course must be the case I unless the solution be diluted with water. My object in subjecting this fluid to a long-continued electric action through the intervention of a porous stone, was to form, if possible, crystals of silica at one of the poles of the buttery, but I failed in accomplishing this by those means. " On the fourteenth day from the commencement of the experiment, I observed, through a lens, a few small whitish excrescences, or nipples, projecting from about the middle of the electrified stone, and nearly under the dropping of the fluid above. On the eighteenth day those projections en-mrged, and seven or eight filaments, each of them longer than the excrescences from which it grew, made their ap-pea ranco on each of the nipples. On the twenty-second day, these appearances were more elevated and distinct, ,md on the twtnty-sixth day,'each figure assumed the fOl'm of a perfect insect, standing erect on a few bristles which formed its tail. Until tilis period I liad no notion that these appearances wei-e any other than an incipient mineral formation : but it was not until the twenty-eighth day, when I plainly perceived these lit tie creatures move' their legs, that I felt any surprise, and I aius owti that when this took place, I was not a little iistoni'Hlicii. I endeavored to detach some from their position on the stone, but they immediately died, and I was obliged to wait patiently for a fow days longer, when they separated tliemaelws from tlic stone and moved about at pleasure, although they had been lor some time after tliir bi-th apparently averse to motion. In the course of a fiew weeks, about a hundred oftem made their appearance on the stone. I observed that at first each of them fixed itself for a considerable time m one spot, appearing, as fkr as I could judge, to feed by suction, but when a ray of lighi hom the sun was directed upon it seemed disturbed, and removed itself to the shaded part of the stone. Out of about a hundred insects, not above five or six were horn on the south side of the stone. I examined some of them with the microscope, and observed that the smaller ones appeared to have only six legs, but the larger ones eight. It seems that they are of the genus Aca-but of a species not hitherto observed. I have had three separate formations of similar fnsects at .dimt times, from fresh portions of the same fluid, v'ith the same apparatus. "As I considered the result of these experiments rather extraordinary, I made some of my friends acquainted with it, among whom were some highly scientific gentlemen, and they plainly perceived the insect in various states. I have never ventured an opinion as to the cause of their birth, and for a very good reason—I was unable to form one. The most simple solution of the problem which occurred to me was that they arose from ova, deposited by insects floating in the air, and that they might possibly be hatched by electric action. Still I could not imagine that an ovum could shoot out filaments, and that those filaments would become bristles; and, moreover, I could not detect, on the closest examination, any remains of a shell. Again, we have no right to assume that electric action is necessary to vitality until such fact shall have been most distinctly proved. I next imagined, as others have done, that they mighi; have originated from the water, and consequently made a close examination of several hundred vessels filled with the same water as that which held in solution the siate of potassa, in the same room, which vessels constituted the cells of a large voltaic battery, used without acid. In none of these vessels could I perceive the trace of an insect of that description. I likewise closely examined the crevices and most dusty part of the room, with no better success. " In the course of the same month, indeed, these insects so increased that when they were strong- enough to leave their moistened birthplace, they issued Olit in different directions, I suppose in quest of food; but they generally huddled together under a card or piece of paper in their neighborhood, as if to avoid light and disturbance. lu the course of my experiments upon other matters, I filled a glass basin with a concentrated solution of silicate of potassa, without acid, in the middle of which I placed a piece of brick, used in the neighborhood for domestic purposes, and consisting mostly of silica. Two wires of platina connected either end of the brick with poles of a voltaic baitory of sixty-three pairs of plates, each about two inches square. After many months' action, silica, in a gelatinous state, formed in some quantity round the bottom of the brick, and as the solution evaporated I replaced it by fresh additions, so that the outside of the glass basin being constantly wet by repeated overflowings, was of course constantly electrified. On this outside, as weU as on the edge of the fluid within, l one day perceived the well known whitish excrescence, with its projecting filaments. In the course of time they increased in number, and as they successively burst into life, the whole table on which the apparatus stood was at last covered with similar insects, which hid themselves wherever they could find a shelter. So-ne of them were of different sizes, there being a considerable diffierence in this respect between the large and smaller; and they were plainly perceptible to the naked eye, as they nimbly crawled from one spot to another. I closely examined the table with a lens, but could perceive no such excrescence as that which marks their incipient state on any part of it. "While these efiects were taking place in my electric room, similar formations were making their apfi; :ir!i,nce in another room, distant from the former. I had here placed on a table three voltaic batteries, -anconnected with one another. The first consisted of twenty pairs of two-inch plati;,s, between the poles of which I placed a glass cylinder fined with a concentrated solution of silicate of potassa, in which was suspended a piece of clay slate by two plat in a wires conn ected "vith either pole of the battery. A piece of paper was placed on the top of the cylinder, to keep out the dust. After many months' action, gelatinous silica in various Ibrrns was electrically attracted to the slate, which it coated in rather a singular manner, unnecessary here to dcscrihe. In the course of time I observed similar insects in their incipicn t, state forming around the edge of the fluid within the jar, which, when perfect, crawled about the inner surface of the paper with great activity. The second battery consisied of twenty paim of cylmders, each equal to a four-mch plate. Between the poles of this I interposed a series of seven glass cylinders, filled with the following concentrated solutions: 1st, nitrate of copper; 2d, subcarbonate of potassa ; 8d, sulphate of copper; 4th, green sulphate of iron; 5th, suljiliatc of zinc; 6th, water acidified with a minute portion of hydrochloric acid ; 7th, water poured on powdered metallic arsenic, reHilng on a copper cup, conn ected with thtjjositive polo of the battery. AB these cylinders were electrified, and united together by arcs of' sheet copper, so that tlw same electric current passed through the whole of them. After many months' action, and consequent formation of certain crystalline mattm-s wliich it is not my object here to notice, I observed sirailar excrescen-ci"s with those before descs'ibed at the cd go of the fluid in every one of the cylinders, excepting the two which contained the carbonate of potiissa and the metallic arsenic; and in due time a host of insects made their o,]iKranec. It was curions to observe the crystallized nitrate and siilplrate of copper, which formed by slow evaporation at the edge of tiio respective solutions, dotted her", and there with the hairy excrescences. At the foot of each of the cylinders I had placed thick paper upon the table, and on lifting them up I found a little colony of insects under each, but no appearand; o f their liavirig been born under their respective papers, or on any part of the table. The third battery consisted of twenty pairs of cylinders, eacli equal to a 8-inch plate. Between the poles of this I intt!"piined likewise a scries of six glass cylinders, filled with various solutions, in only one of which I obtained the insect. This contained a solution of silicate of potassa. A bent iron wire, one fifth of an inch in diameter, in the form of an inverted siphon, was plunged some inches in this solution, and connected it s'ith the positive pole, while a small coil of fine silver wire joined it with the negative. This instrument is represented in Fig. 2. " I have obtained the insects on a bare platina wire, plunged into fluo-slllcic acid, one inch below the stirface of the flttid, at the negative pole of a small battery of two-inch plates, in cells filled with water. This is a somewhat singular fluid for these insects to breed in, who seem to have a fl.inty taste, although they are by no means confined to silicious fluids. This fluo-silicic acid was procured from London some time since, and consequently madc! of London water, so tha the idea of their being natives of the Broomfidd water is quite set aside by this result. " The apparatus wag arranged as follows: Fig. 33, a glass basin (a pint one), pmt fille,i with fluci-silicic acid to the level. A 13 is a small porous pmj, made of the same materials as a garden-pot, partly filled with tho same acid to the leve1, B, with an earthen cover, C, placed upon it, to keej) out tlie light, dust, etc. D is a platina wire connected with the positive pole of the battery, with the other end plunged into the acid in the pan, and twisted around a piece of ccimiion cjuartz ; on which quartz, after many months' action, are forming singularly beautiful and perfect-formed crystals of a transparent substance. not yet analyzed . as they are still growing. These crystals are of the modification of the cube, and are of twelve or fourteen sides. The platina wire passes under the cover of the pan; E is a platina, wire count ;ctcd with the negative pole of the same battery, with the other end dipping into the basin, an inch or two below the fluid, and, as well as tlu; other, around a piece of quartz. By this ai-rangement it is evident that the electric fluid enters the porous pan by the wire, D, percolates the pan, and passes out by the wire, E. It is now upward of six or eight months (I cannot at this moment put my hand on tho memorandum of the date) since this apparatus has been in action, and though I have occasionally lifted out the wire to examine them by a lens, yet it was not till the other day that I perceived an insect, and there are now three of the same insects in their incipient state, appcM-ing on the naked platlna wire at the bottom of the quartz in the glass basin of the negative pole. These insects are very perceptible, and may be represented thus (magnified) : in Fig. 4, A is the platina wire,B the quartz, and C the incipient insects. It should be observed that the g-hss basin, Fig. 3, has always been loosely covered with paper. The incipient si.p-pearance of the insects lias already been described. The iH-aments which project are in course of time seen to move before the ])( rf,'ct insect detaches itself from the birth place. Fig. 5 shows the insects in their various states, magnified." Brain Worked Manual Labor. Our excellent cotempomry, tlw IleraM of Health,, thus discourses on the combining of mental and physical toroo to the relief of both mind and body:—" The worker with his brains would love brain work more if he bad a couple hours of hand work to do every day. If such persons could Imve their gardens and shops to run to when their heads were tired, they would soon recuperate, and the muscular toil not being in excess would soon be a delight. If, on the other hand, the toiler with the hand could do daily some mental labor, it would add greatly to his happiness. The sharpening of the brain by culture would add effectiveness to the hand. The reason for this, is because man is a composite bein g. His muscles wore not made for non-use more than his brain, and the right HSB of each is a pleasure and not a pain. After a frw generations wlJ siall hfive what is now the pfayei of thousands, more culture for the laboring man, and more phy-,lical labor for the cultured man. This will establish a harmony between the two, which will add greatly to the prosperity, happiness, and health of both."