Professor O. C. Marsh, of New Haven, recently delivered before the American Association for the Advancement of Science an address on the " Introduction and Succession of Vertebrate Life in America. " According to present knowledge, he stated, no vertebrate life is known to have existed on this continent in the archrean, Cambrian, and silurian periods, yet during this time more than half the thickness of American stratified rock was deposited. Fishes are known in the upper silurian of Europe, however, and there is therefore a probability that they will be yet discovered in our strata of the same age, if not at a still lower horizon. Passing through the various geological periods, Professor Marsh noted the extinction or increase of various orders of fishes, and then, referring to the amphibia, stated that the latter are so nearly ' allied to the ganoid fishes as to leave little doubt, of their descent from some member of that group. The earliest evidence of their existence on this continent is in the sub-carboniferous, where footprints have been found which probably were made by labyrinthodotits, the most ancient representatives of the class. OEIGIN OF THE BIRDS. During the mesozoic period some of the strangest forms of reptilian life made their appearance and became extinct. Then came the dinosaurs, true reptiles, yet having characteristics peculiar to birds of the ostrich order, so that it is possible that they were the parent stock of all birds. Professor Marsh's account of the great saurian monsters of the cretaceous strata is wonderfully interesting. He told of vast lizards, some sixty f!"et in length, which inhabited the inland cretaceous sea when the Rocky Mountains were just begin-ing to rise above the waters. In a valley of this old ocean bed he had seen seven different skeletons of these monsters in sight at once. There were-also the huge . plerosauria, the veritable dragons, having a spread of wings of from ten to twenty-five feet, and one colossal dinosaur, when erect, stood thirty feet in height. BIRDS WITH TEETH existed in that strange world. The aquatic hesperornis, nearly six feet in height, had teeth set in grooves in its jaws. It was a carnivorous, swimming ostrich. The ichthyornis, a small flying bird, had teeth set in sockets, while strange enough, the companions of these ancient toothed birds were pterodactyls, without teeth. There came a period at last when the dinosaurs and other mesozoic vertebrates disappeared, and mammals henceforth became the dominant type. Then lived a great sloth, which, after the elevation of the Isthmus of Panama, crossed over from the northern to the southern continent of America. there found a more congenial home, and there in time became extinct. In . the middle eocene, west of the Rocky Mountains, THE DINOCERATA, a remarkable group of ungulates, made its appearance. Nearly equalling the elephant in size, this animal had shorter limbs, while arming its skull were two or three pairs of horn cores, besides enormous canine tusks. In the lower eocene appeared the progenitor of the horse, the eohippus, about the size of a fox and havingwell developed toes. In the lowest eocene appear the artrodactyles, the ancestor of the pig, and in the upper eocene comes the oromeryx, whence probably sprang the deer. THE PRIMATES AND MAN. We. come now to the highest group of mammals, the primates, which includes the lemurs, the apes, and man. This order has a great antiquity, and even at the base of the eocene we find it represented by several genera belonging to the lower forms of the group. In considering these interesting fossils, it is important to have in mind that the lemurs, which are usually regarded as primates, although at the bottom of the scale, are only found at the present day in Madagascar and the adjacent regions of the globe. All the American monkeys, moreover, belong to one group, much above the lemurs, while the Old World apes are higher still, and most nearly approach man. In the lower eocene of New Mexico we find a few representatives of the earliest known primates, and among them are the genera lemuraVUS and limfiotherium, each the type of a distinct family. The oldest known remains of man on this continent differ in no important characters from the bones of the typical Indian, although in some minor details they indicate a much more primitive race. These early remains, some of which are true fossils, resemble much more closely the corresponding parts of the highest Old World apes, than do the latter our tertiary primates, or even the recent American monkeys. Various living and fossil forms of Old World primates fill up essentially the latter gap. The lesser gap between the primitive man of America and the anthropoid apes is partially closed by still lower forms of men, and doubtless also by higher apes, now extinct. The real progress of mammalian life in America, from the beginning of the tertiary to the present, is well illustrated by the brain-growth, in which we have the key to many other changes. The earliest known tertiary mammals all had very emajl-brains, and in some forms this organ was proportionately less than in ce'rtain reptiles. There was a gradual increase in the size of the brain during this period, and it is interesting to find that this' growth was mainly confined to the cerebral hemispheres, or higher portion of the brain. In most groups of mammals the brain has gradually become more convoluted and thus increased in quality as well as quantity. In some, also, the cerebellum and olfactory lobes, the lower parts of brain, have even diminished in size. In the long struggle for existence during the tertiary time the big brains won, then as now; and the increasing power thus gained rendered useless many structures inherited from primitive ancestors, but no longer adapted to new conditions. Another of the. interesting changes in mammals during tertiary time was in the teeth, which were gradually modified with other parts of the structure. The primitive form of tooth was clearly a cone, and all others are derived from this. All classes of vertebrates below mammals, namely, fishes, amphibians, reptiles, and birds, have conical teeth, if any, or some simple modification of this form. The edentates and cetaceans with teeth retain this type, except the zJeUglo-donts, which approach the dentition of aquatic carnivores. In the higher mammals, the incisors and canines retain the conical" shape, and the premolars have only in part been transformed. The latter gradually change to the more complicated molar pattern, and hence are not reduced molars, but transition forms from the cone to more complex types. Most of the early tertiary mammals had forty-four teeth, and in the oldest forms the premolars were all unlike'the molars; while the crowns were short, covered with enamel, and with out cement. Each stage' of progress in the differentiation of the animal was, as a rule, marked by a change in the teeth ; one of the most common being the transfer, in form at least, of a premolar to the molar series, and a gradual lengthening of the crown. Hence, it is often easy to decide . from a fragment of a jaw to what hOl;izon .of the tertiary it belongs. The fossil horses of this period, for example, gained a grinding tooth, for each toe they lost, one in each epoch. In tie single-toed existing horses, all the premolars are like the molars, and the process is at an end. Other dental transformations are of equal interest,- Out this illustration must suffice. The changes in the limbs and feet of mammals, during the same period, were quite as marked. The footof the primitive mammal was doubtless plantigrade, and certainly five-toed. Many of the early tertiary forms show this feature, which is.still seen in some existing forms. This generalized foot became modified by a gradual loss of the outer toes, and increase in size of the central ones ; the reduction proceeding according to systematic methods, differing in each group. Corresponding changes took place in the limb bones. One result was a great increase in speed, as the power was applied so as to act only in the plane of motion. The . best effect of this specialization is seen to-day in the horse and antelope, each representing a distinct group of ungulates, with five-toed ancestors. THE sharpening angle of ordinary soft wood planing ma chine irons should be about 35 degrees, and for hard wood tool cutters, 50 to 55 degrees. The Uses of Fish Skins. Although the skin of some marine mammals, such as those of the seal, walrus, and the white whale or beluga (known as porpoise leather), have long been commercially employed, it is only lately that attention has been more generally directed to the utilization of fish skins on an extended scale. Their employment hitherto has been very limited. Eel skins have been used for the thongs of whips and the attachments of flails, dried sole skins to clarify coffee, and some shark and ray skins by workmen to smooth and polish substances, and also to make a kind of shagreen leather. At the Maritime Exhibition held at the Westminster Aquarium this year Mr. G. Kent, of Christiana, Norway, exhibited a variety of tanned skins, among which were: 1. Whale skins tanned; the. size ranges from 12 inches broad by 60 feet in length, suitable for wheel bands, for driving machinery, etc. 2. White flsh, for upper leather, which can be prepared in pieces of 12 feet by four feet. 3 Skins. of various flat fish, dressed and prepared for gloves. Fine upper leather can be made, often to be had in sizes up to 3 feet square. 4. Skins of soles, dressed and tanned suitable for purses, etc. 5. Skins of thornbacks, suitable for cabinet makers instead of sand paper, and very much more durable. 6. Skins of eels, dressed and dyed, suitable for braces and other purposes. In Mon. Chas. Varey's "Scientifique Correspondence" from Paris, of August 7, mention is made of an industry carried on at Colburn, in Canada, in the skins of species of silurids for glove making, and this is to be prosecuted on a larger scale, both for the flesh for salting and the skin for currying. Shoes have been made in Gloucester, Massachusetts, from the skins of the cusk or torsk {Brosmuus vulgaWf'ig), the use of which has been patented. If this material for shoes proves what it promises, it will open up a new market for fish skins, which .will no doubt be highly profitable. In Egypt, flsh skins from the Red Sea are used for soles of shoes. In theJAnimal Products Collection at the Bethnal Green Museum there are some tanned sole skins shown. The skin of the losh or burbot (Lota maculata), cleansed, stretched, and dried, is used by country people in many parts of Russia and Siberia to trim their dresses, and instead of glass for the windows of their dwellings, being as transparent as oiled paper. It is also utilized by some of the Tartar tribes, as material for. their summer dresses, and the bags in which they pack their animal skins. The inhabitants of the eastern coasts of the middle of Asia clothe themselves with the tanned skins of the salmon. It is asserted that it makes a leather as tough as wash leather. The scale marks give. a very neat pattern to the leather. W. Brozowsky, in his "Waarenkunde," Vienna, 1869, under ' Fish Skin," says it is obtained from the sea angel (Squalus squatina, Lin. ; Squatina Imvis, Cuv.), the thorny shark {Squalus acantkias, Sq. carcharias), the tigered shark Sq. caniculata), and some skates, as the angel skate (Baja rhinobatis) RaJo Sephen, etc. The skins of these skates and sharks have spines of different sizes instead of scales. The skins are used for polishing, and, after the star-formed spines have been smoothed down with sandstone, for covering boxes and cases, etc.. ' The "Waaren Lexicon" of .T. C. Schedel enumerates the following fishes : Sea dog (Squalus blainvellei, Riss, Aiguillat, Blain), Sq. aranthias, and other small sorts, Sq. carcharias, Lin., Sq. canicula, and Sq. catullus. . Guibourt (sixth edition, by Dr. G. Planchon, 1870-71, vol. iv.), says, "The sephen of the Red and Indian seas, belonging to the genus Tygon, produces the tuberculous and hard skin called galuchat, after the name of a Paris workman who employed it first. The greater part of the selacians, namely, the roussettes, sharks, humantins, aigul-lats, leiches, etc., have a rough skin, which is used for covering boxes, and also for polishing wood. The greatest confusion exists among merchants as to the names given to the different skins. Each tradesman applies, acpording to his fancy, the name of peau de requin, peau de chien de mer, chagrin and even galuchat. I endeavored to obtain specimens of the various skins,_ in order, if possible, to determine the species. "1. Shark skin, from a young shark; small,' imbricated scales, somewhat translucid, with longitudinal lines, the borders or edge entire and circular. The edge is free on the body, but attached on the fins. The skin serves for covering cases, etc., but is not rough enough for polishing. "2. Skin of mottled roussette (a-yllium, Cuv.). Tuberculous, imbricated, horny, fine and hard scales, very near one to the other, and transparent, each triangular. Skin much used for polishing. Some persons state that ' false galuchat' is made of it by rubbing off the scales, which leaves a square figure that becomes very showy when the skin is applied on a green paper. I rather believe (continues M. Guibourt) that the false galuchat is made with the skin of the aiguillat. " 3. Peau de leiche (ymnus), sold to cabinet makers under the name of peau de chien de mer, is covered with nearly rhomboid tuberculous semi-transparent scales, arranged one near the other in quincunxes. " 4. Peau d'aiguillat (Spinax acanthias, 'Cuv.). Viewed with a magnifying glass, this skin appears covered with small square opaline scales, not rough .like the preceding, but much used by the 'gainiers' or sheatli makers, for its glossy nacreous aspect. ' 5. Peau de sagri (Spinax niger, Cuv.). Same uses as the preceding. The word gri is Persian ; SagAer, Turkish, from its resemblance to the dressed leather made from the mule and ass, whence our word shagreen. " 6. Galuchat or sephen skin, from the back of the Tgon sephen, Oloq.. It has numerous round tubercles, which become white by rubbing down, and in the interior opaque and nacreous. The skin is sometimes dyed for different colors, but it is often preferable to leave it the natural color by only half polishing it." The quantity of ray skins,. dried or salted, imported into France in 1863 was about 18,000 Ibs. weight, principally from Portugal. Formerly they used to fetch as high as 7 francs the pound, now they may be had for Is. a pound. The best galuchat, or what we should call shagreen, is-mad'e from the skin of the sephen, which abounds in the . Mediterranean Sea, and is also met with in the Red Sea and the Indian Ocean. This skin is remarkable for the size of the osseous protuberances. There are however two kinds of these rays, one with rough skin and the other with smooth. From a certain portion of the skin of the angel shark (Squatina angelus) the Turks make the most beautiful sea-green watch cases. These- sharks, which form a connecting link between the genera of rays and sharks, are found in the Mediterranean principally, and'the German Ocean sometimes. The skin being very rough, it is employed to polish wood and ivory, as well as for other uses in the arts. Turners, ebonists, and carpenters in Europe use the rough skin of the blue dog fish (Squalus glaucus, Linn.) like emery paper, for smoothing their work and preparing it for polishing. This shark skin is also used by the native workmen of the East for polishing wood and ivory, and it is made into shagreen. The best is that obtained from the Rai Sepplien of India and the Red Sea. That most used now seems to be the skin of the ray (Hypolophus Sephen) which is very common on the Malabar coast, and an extensive commerce is now carried on in them in the Indian Ocean; they are found in the Sea of Oman, and also taken at Mahe. The house of Giraudon, 48 Rue Molire, Paris, makes excellent use of them for morocco and tabletterie. Peau de Roussette (Squalus catulus and canieulus, Lin.). This fish, called chat at Marseilles, and crin in Catalonia, is' smaller than the angel fish. The skin, reddish and -without spots, is of a uniform grain, flat, and only used to make cases and other articles known' as shagreen. These skins come from the Mediterranean, and are imported in bundles by the sailors, selling, according to size, from 30s. to 36s. thedozen. Peau de chien de mer is another name given in France to some species of Squalus or requin. That usually found on the French coasts. is known under the naines of chien marin, chat marin, roussette tigree {Squalus catulus, Linn.). Turners, cabinet makers, and carpenters use the skin for scraping and smoothing their work before polishing; metal workers and others also use it. This skin, when worked up with the tubercules with which it is studded, takes the name of galuchat, and is ordinarily dyed green, to cover cases, sheaths, and boxes. Under the name of chagrin these skins used to be much employed in Turkey, Syria, Tunis, and Tripoli.- That made in Constantinople 'was considered the best. It was colored black, green, white, and red.--Itu P. L. Simmonds, in the Journal of tie Society of Arts. Rules Cor Calculating the Speed of Pulley s. The diameter of the driven being given, to 'find its number of revolutions : Rwfe--Multiply the. diameter of the driver by its number of revolutions, and divide the product by the diameter of the driven; the quotient will be the number of revolutions of the driven. .--24 inches diameter of driverx150, number of revo-lutions,=3,600+12 inches diameter of driven=300. The diameter and revolutions of the driver being given, to find the diameter of the driven, that shall make any giten number of revolutions in the same time: . Rule--Multiply the diameter of the driver by its number. of revolutions, and divide the product by the number of required revolutions of the driven; the quotient will be its diameter. --Diameter of .driver (as before) 24 inchesxrevolutions 150=3,600. Number of revolutions of driven required=300 I'hen-3,600+300=12 inches. The rules following are but changes of the same, and will be readily understood from the foregoing examples. To ascertain the size of the driver: Multiply the diameter of the driven by the number of revolutions you wish to make, and divide the product by the required revolutions of the driver; the quotient will be the size of the driver. To ascertain the size of pulleys for given speed: Rule-Multiply all the 'diameters of the drivers together and all the diameters of the driven together; divide the .drivers by the driven ; the answer multiply by the known revolutions of main shaft. FiLL-qG FOR CRACKED . CEILINGS.--Whiting mixed with glue water or calcined plaster and water makes a good putty for fining cracks in plastered ceilings. BLACK WALNUT STAIN.--Asphaltum thinned with turpentine will. stain a beautiful .black walnut color. It must be i varnished over.