The toad is of a retiring di sposition, loving dark corners and shady places. It has a slow, crawling motion, and is of a very timid disposition. Numerous instances might be cited of pet toad s, and of their becomitigg quite tame. The toad differs in some respects from the nearly related frog. The of the mouth is, however nearly the same. The tongue is attached by the root, as it were, to the base and front of the mouth, the tip being reversed and pointing down the throat when the animal is at rest. The moment it seeS an insect its eyes brighten and sparkle, the toes twitch, and quicker than the eye can fol low, th e tongue is thrown out, the insect transfixed, and withdrawn into the mouth. Unlike the frog, the toad does not spring after its prey, but remain s seated. Having kept frog,s in the aquarium, I have noticed that they will spring two or three times their own length from the mose to catch a fly on the glass, using their tongue, as it were, on the jump. They seldom miss their mark. As far as my experience goes, neither of these animals will eat anything without lite or motion. I have, however, often deceived a frog by moving a dead fiy in the sight of the creature, which it always took readily. Many stories have been told of toads in rocks, and reasons have been given by authors as to the way in which they have become so embedded. My subject has, however, nothing to do with these " old great toads," but to one of our own day and generation. After this digression, I shall now introduce my friend, the toad, in his capacity as a collector of beetles. The true naturalist, in the pursuit of his study, is a very teachable individual ; he never refuses assistance from any one, whatever his station in life is, or however meager his knowledge of the science may be. The m any ways ha uses the animal creation to advance his knowledge, in the particular branch of study, may be illustrated as follows : The conchologist wearies for the pleasant days of summer, to take a trip to the sea-side, with his dredges and lines, his bottles and store-boxes, where he adds to his collection many interesting and perhaps new forms of molluscan life. A trip to the sea-side is not always easily obtained ; but the naturalist may be seen in the market buying the several species of flat fish, stich as flounders and other species which live and feed at the bottom of the sea. Knowing them to be good collectors, he takes advantage of th is fact to procure many and sometimes rare species, and thus adds to his cabinet, without the trouble of dredging for them. The entomologist, likewise, has recoarse to different methods to obtain the object of his interesting study. The following is one of many : Starting at six o'clock one morning, in the summer of 1864, for a walk to our beautiful mountain, to collect insects, provided with the requisite apparatus, a wide-mouthed bottle, with spirits, for beetles, and a small flat box, lined with cork, for butterflies, etc., my success was particularly good. The first captures were eleven specimen of carrion beetles, comprising three species, viz., SUpha pdtata, marginales, and itiquaiia. These were obtained from the body of a dead hawk-owl Surrnia. ulala). Having secured them in the bottle, and walking leisurely along. I noticed a toad (Bufo Americcanus) sitting content edly at the root of a basswood-tree TUia Americana). Having never made use of my dingy friend as an insect-collector, although aware of his propensity that way, my mind was made up to press him into the sTOce-,but how ? He must be dead first. As he sat looking at me with his beautiful eyes (for although his appearance is not very prepossessing still those beautiful, bright, yet lan gid eyes go a great way to improve his appearance), I had certain qualms of conscience about taking life ; still it was in the cause of entomology, and for the' furtherance of, science his life was' sacrificed. Now he was dead ; how was I to proceed ? I had cut up and dissected many insects as well as birds, but to cut up a toad, and before breakfast—" there's the rub "—that gray, warty toad, no beautiful eyes now. One slash of the knife through the skin, another through the wall:! of the stomach, and the poor creature's breakfast was exposed. I was a little disappointed at first, as one or two common forms of beetles presented themselves, that might have been obtai ned without sacrificing the poor animal ; stll, I reasoned as he had been up nearly, or perhaps all night, collecting, and I had not, he must have taken some species not in my collection. Having scraped the contents of his stomach into my bottle of spirits, I started home, resolved to see what the insects were before breakfast. I spread them out on a sheet of blotting paper and counted them ; the result being thirteen perfect specimens. I have killed several toads since, with similar results ; one, I may mention, had the stomach filled with a species of Chry-melid, Doryphwra trirvlata, amounting to eleven specimens. He had evidently come across a colony of that insect, and made a hearty breakfast. I may state that this insect was in great abundance, during 1864, on the Island of Mon treal. The same may be said of last summer, 1868 ; taking them by the score on the Mountain, along the river at Hochelaga. The earlier you go out in the morning the better ; before sunrise, if possible, before the process of digestion has gone too far. Latent Meat of Metals. The quantity of heat latent in the metals, and which becomes apparent when they are compressed, is admirably illustrated by the faint flash of light which is emitted when a bullet from a steam gun strikes a wrought-iron target. The bullets are completely flattened, and when directed against a plate of lead placed in front of the target, the two surfaces of lead become firmly united as if melted or soldered together. The flash of light is OIlly visible in a darkened room. Another still more striking illustration is seen in the flash of light produced when the 80-1b. hexagonal bolts fired from the Whitworth gun strike the thick iron-plated sides of a floating battery : " Notwithstanding the immense resisting power of the iron plates, the hexagonal bolt passed completely through them. The shot when discovered was fouid to be so hot that no one could touch it, and was ascertained to have been compressed to the ext ent of an inch in length. It Was noticed that at the instant of concussion between the shot and the vessel, a broad sheet of intensely bright flame was emitted, almost as if a gun had been fired from the vessel in reply." The same effect has been repeatedly noticed when the balls from the heavy Dahlgren guns of the monitors struck the stone fortifications against which they were directed. The beat, in these cases, was that previously latent in the iron, made sensible by the compression of the metal and the diminution of its specific heat. . In like manner, the intense heat which is evolved when iron bars are subjected to the process of rolling, and not unfrequently by the axles of cars and carriages when in rapid motion, and in the processes of bo-ing and planing metals, is due to the same cause. It is the heat previously latent in the mals, evolved and conv;rted into heat of temperature by the diminution of their specific heat in consequence of compression. The heat set free in th e simple operation of boring a hole with a gimlet, is sufficient to inflame a friction match. The heat 'produced by the rapid drawing of a string tightly around the neck of a glass flask, is sufficient to crack it. And in the whale fishery, the heat evolved by the inconceivably rapid motion of the rope over the side of the boat, after the whale is struck, would be sufficient to set it on fire if it were not kept cool by the continual pouring of cold water. In the best constructed steam en-gin es, the bewings of the shafts are made hollow, .and a stead y stream of cold water caused to circulate through them, in order to prevent them from becoming excessively heated, and the axles from elfpanding to such a degree as to bo incapable of moving. These are illustration s of a general principle. Whenever any body is expanded, heat is absorbed and temperature sinks. Whenever any bo ly is compressed, latent heat is given out and temperature rises. This is true of solids, liquids, and gases. Liquids, if compressed, grow warm ; if relieved from compression, they grow cold again. Gases, if compressed, grow hot ; if released from compression, temperature declines. So, in like manner, when bodies change from the solid to the liquid or gaseous state, there is an absorption of heat, because of the large amount which is expended in making the change. The diffiarence between the same substance as a solid and as a liquid, is, that in the latter case the particles are so far removed that they can slip readily upon each other. This separation can only by maintained by the addition of a large amount of heat. Conse-queatly, whenever a solid is liquefied there is an immense absorption of heat, and temperature sinks ; whenever a liquid is solidified. the reverse takes place and temperature rises. The latent heat, no longer required, becomes sensible. When a liquid is vaporized, heat is absorbed, and temperature sinks. When a vapor is condensed into a liquid latent heat is given. out, and temperature rises.—P1Jmclwn's Ohemical Forces. What a Man Knows. What a man can write out clearly, correctly, and briefly, without book or reference of any kind, that he undoubtedly know s, whatever else he may be ignorant of. For kBowledge that falls short of that—knowledge that is vague, hazy, in. distinct, uncertain—I for one profess no respect at all. And I believe there never was a time or country where tho influences of careful training were in that respect more needed. Men live in haste, write in haste—I was going to say think in haste, only that the word thinking is hardly applicable to that large number who, for the most part, pUrchase their daily allowance of thought ready made. You find ten times more people now than ever before who can string words together,with facility, and with a general idea of theii- meaning, and are ready with a theory of some kind about most matters. All that is very well as far as it goes, But it is one thing to be able to do this and quite another to know how to use words as they should be used, or really to have thought out the subject which you discuss.—Lord Stanley. An Ingenions Method Cor Drying Vegetable Ilild Animal Substances. A method recently adopted for drying vegetable and animal substances, consists in filling a vessel half full with fused chloride of calcium, pouring ether upon it, and then placing above it a ves6el containing the material to be dried. The vessel is placed upon a glass plate, and over this a bell glass, fitting completely to its surface. TThe chloride of calcium abstracts the moisture from the ether, whiCi then constantly takes away a new quantity from the 8ubstance in the vessel-above, until it is quite dry. Articles dried in this manner have quite a different appearance from these from which tho moisture is removed by the ordinary process ; vegetables retaining their natural color, and animal substances their elas-tit'ity and flexibility. WHAT CAN You DO BETTBR ?—Young men out of c'ploy. ment cannot do better than to send to this office fo!: a prospectus and go about soliciting subscribers for the SCIBNTIPIC AMBEICAN. The sum of fifteen hundred dollali'S cash is to be paid for the fifteen largest' lists of naUlel!l received withi the money, at this office, hefoM Febrq\\l1 1:0v 1870.