gest one improvement, which occurred to us on the perusal of his description. We think that the broad wheel, E, could not be made to work delicately or correctly into the other two wheels, D and F, because the number of teeth in both is not the same; hence, the teeth must be thicker, or the spaces greater in the one than in the other: we would therefore suggest, that two wheels of 36 teeth, be made to correspond to the two different wheels, D and F, and then fastened firmly together, so as to make but one wheel equivalent to the broad wheel, E. Perhaps other improvements may occur to some of our readers, which we shall be glad they will communicate to us. For the sake of those who are not much acquainted with this subject, we insert the following notice respecting the construction of the clocks to which our Correspondent has referred.

Dr. Franklin contrived his clock to show the hours, minutes, and seconds, with only three wheels and two pinions in the whole movement. The dial-plate had the hours engraven on it, in spiral spaces, along two diameters of a circle, containing four times 60 minutes. The index goes round in four hours, and points out the minutes from any hour which it has passed to the next following hour. The small hand, in arch at top, goes round once in a minute, and shows the seconds. The clock is wound up by a line going over a pulley, on the axis of the great wheel, like a common thirty-hour clock. Many of these very simple machines have since been constructed, that measure time exceedingly well. This clock is subject, however, to the inconvenience of requiring frequent winding up, by raising the weight, as also, to some uncertainty as to the particular hour shown by the index.

Mr. Fergusson proposed to remedy these inconveniences by another construction, which is described in his Select Exercises. His clock will go a week without winding, and always shows the precise hour; but, as he acknowledges, it has two disadvantages which do not belong to Dr. Franklin's clock. When the minute hand is adjusted, the hour plate must also be set right by means of a pin; and the smallness of the teeth in the pendulum wheel will cause the pendulum ball to describe but small arcs in its vibrations; and, therefore, the momentum of the ball will be less, and the times of the vibrations will be more affected by any unequal impulse of the pendulum wheel on the pallets. Besides, the weight of the flat ring, on which the seconds are engraven, will load the pivots of the axis of the pendulum wheel, with a great deal of friction, which ought, by all possible means, to be avoided. To remedy this inconvenience, the seconds plate might be omitted.

Mr. Fergusson also contrived a clock, showing the apparent diurnal motions of the sun and moon, the age and phases of the moon, with the time of her coming to the meridian, and the times of high and low water; all this being added to the clock, by having only two wheels and a pinion added to the In this clock,

common movement.

the figure of the sun serves as an hour-index, by going round the dial in 24 hours; and a figure of the moon goes round in 24 hours, 50 minutes, the period of her revolution in the heavens, from any meridian, to the same meridian again. A clock of this kind was adapted by Mr. F. to the movement of an old watch. He also gives, in the same work, a description and drawing of an astronomical clock, showing the apparent

daily motions of the sun, moon, and stars, with the times of their rising, southing, and setting; the

places of the sun and moon in the ecliptic, and the age and phases of the moon for every day in the year.

A GOLD-BEATER having melted a quantity of fine gold, beats it, on his anvil, into a plate as thin as paper, then cuts it with his shears, into little pieces about an inch square. These he puts between the leaves of a sort of book made of vellum, and, with a hammer, beats them, on a marble block, till they are stretched nearly to the size of the book. He then takes them out, cuts them in four, and puts them into another book, to be farther extended in the same way. When they are brought to a certain degree of fineness in the two first books, they are again cut into four, and made to undergo the same hammering in two others, which, as well as the former, are called moulds; but the leaves of these, instead of vellum, are made of oxguts, well scoured and prepared for that purpose. The leaves of gold being beaten to the thinness required, which is greater or less, according to the use for which it is intended, are disposed in little paper books, prepared with red bole, to cause the gold to stick; and thus they are kept for sale. By this operation, an ounce of gold is beat into a surface of one hundred and forty-four square feet; and it has been computed, that the thinnest parts of some gold leaves are scarcely one 360,000dth part of an inch thick.

But the distension of gold under the hammer is inconsiderable, when compared with what it undergoes in the drawing iron. What we call gold wire is made of a cylindrical ingot of silver, usually about two feet long, and two or three inches, round, which, being covered with

leaf-gold, is successively drawn through the holes of several irons, each smaller and smaller, till it be as fine, or finer, than a hair of the head. The ingot passes through a hundred and forty, or fifty, holes before it is brought to its utmost fineness, every new hole lessening its diameter; but, then, it gains in length what it loses in thickness, and, consequently, increases in surface, yet, the thin covering of gold still follows the silver in all its extension, and never leaves the minutest part bare, even to the microscope. Mr. Reaumur, who has been very curious in his calculations respecting the ductility of gold, observes, that an ingot, or roll, of silver, weighing thirty pounds, about an inch and a half in diameter, and twenty-two inches long, is usually covered over by the wire-drawers with two ounces of leaf-gold, and sometimes with little more than one; so that the thickness of the gold seldom exceeds a five-hundredth part of an inch, and sometimes not a thousandth part.

The same ingenious philosopher found, by exact weighing, and the most accurate computation, that an ounce of the fine wire drawn from such an ingot, covered with two ounces of gold, was 3,232 feet long, and, consequently, the whole ingot, 1,163,520 feet, Paris measure; which are equal to 1,264,400 English feet, or 240 miles. But this is not all: for the greatest part of our gold wire is spun or wound, on silk; for which purpose, it is pressed flat between two rollers of well-polished steel, and, by this pressure, it is lengthened about one

seventh; so that, instead of 240 miles, we may now reckon 274. The breadth of this thin lamina, is a 96th part of an inch; and, by calculation, it appears that an ounce of gold is thus spread into a furface of 1190 square feet; whereas, by the gold-beater's hammer, it is only extended to 146, as before mentioned.

Amazing as this appears, the gold may still be reduced to much more excessive thinness, by repeating the pressure between the steel rollers, and yet remain a perfect covering for the silver, so that the best eye, even assisted by the best microscope, cannot discern the least chasm or discontinuity. D.

ON Monday, January 12th, Mr. McFadyen delivered his introductory lecture on Natural History, in the hall of the Mechanics' Institution. We confess, we felt no small degree of anxiety, as to the manner in which he would acquit himself, in this his first public appearance. Not that we harboured the least doubt of his abilities being sufficient to carry him through with eclat, but we considered that he was deprived of many of the advantages of a practised lecturer, and, consequently, subjected to all the inconveniences, which inexperience and want of confidence inevitably inspired. We had few fears of this nature with regard to Mr. Steele. In appearing before an assembly, he was in his element. He was merely in a situation to which long practice had habituated him; and we must do him the justice to say, that he acquitted himself as well as it was possible for a man to do.

We were prepared to concede a good deal to Mr. M'Fadyen, but he had no need of our indulgence. On the contrary, his introductory lecture exhibited all the skill of an adept in composition, all the imagination of a rich and vigorous temperament, and all the enthusiasm of an ardent votary of science. We must say, that we never expected to hear within the walls of this institution, such a fine mixture of philosophy, fancy, and learning. It was

not merely the dry details of abstract science that were embodied together. These were blended with the most beautiful and appropriate reflections, and the whole preserved in perfect keeping and harmony. He gave the following elegant and original view of the origin of the science, in nearly the following

terms:

"The origin of Natural History we may trace to some fortuitous circumstance-to some phenomenon accidentally observed. Thus he is to be regarded as the founder of Astronomy, who, amid his flocks on the plains of Chaldea or India, first discovered the erratic nature of the planets, and he is to be regarded, as having made the first steps in Mineralogy, who returned from the mountains with some beautiful crystal, to adorn the rude cave that sheltered him. He also was the first Zoologist, who, in the chase, first learned to distinguish the various habits and manners of the forest families, and she was the first Botanist, whose gentler spirit first took delight in the cultivation of flowers."

He then gave a general view of the form, density, and structure of the earth; and, in speaking of the utility of the science, stated the following facts, which we are sure our readers will duly appreciate after their perusal.

"From an ignorance of the po

sition of strata, landed proprietors have often remained unacquainted with that wealth which lay within their reach. Thus, an estate in Derbyshire was lately sold, which has since been found to contain one of the richest lead mines in the world; and, in the same county, the valuable ores of zinc were for a long period employed in mending the public roads.'

The

He afterwards glanced at the antediluvian period of the globe, and detailed many highly interesting facts connected with that era. portion of the earth now inhabited, was at one period covered by the ocean; and, by a natural consequence, he inferred, that the portion now covered by the waters was formerly dry land. In support of the former fact, he mentioned some very singular circumstances. Marine productions have been found on Mount Perdu in the Pyrenees, at the height of 10,500 feet; also, on the Andes, at an elevation of 14,000 feet, and along the whole tract of the Appenines. On this subject he made the following beautiful reflections:

"This inquiry carries us back to the infancy of our planet, when chaos and darkness brooded over all, and our continents and loftiest mountains were still covered by the waters. We can call up the idea of that period-those days of solitude and desolation, when nature was the prey of contending elements, and we can imagine the dreary intervals of repose, with which such disturbed periods were succeeded, when all was one vast solitude-one lifeless desert, in which the voice of no creature was heard; when the polypi, and the imperfectly organized products of the ocean, were the only living inhabitants of the globe. From that, we pass to a later period, when continents began to rise, and

their exposed surfaces to be covered with the first verdure of vegetation, and with the primeval forests of these early ages, when the deep silence of nature was first broken by the voice of the majestic Mastodon, and the nightly Mammoth, which, for a season, were lords of all, but at length perished in the great revolution which preceded the creation of our race."

After detailing many singular facts, Mr. M'Fadyen gave a sketch of the influence of time upon the face of the earth. In the course of ages, the mountains wear away, and at one period must have been much loftier than they are at present. The Pyrenees are said to lose a foot in a century. He then illusstrated generally, the slow but sure progress which the ocean is constantly making in altering the face of the globe. The next subject at which he glanced, was a rapid outline of volcanos and earthquakes. This part of the lecture was written with great spirit and elegance; but perhaps the best of the whole, was what related to coral islands. We could not have thought it practicable to render such a subject so highly interesting. The conclusion of the lecture, was occupied in alluding to the various races of animals which have disappeared from the earth, and in giving a general survey of the utility of the science to all classes of society.

We are thus particular in speaking of this introductory lecture, because we consider it far, very far, above the ordinary run of such productions, and an earnest of what the remainder of the course may be. A merely scientific man could not have written it. It contains more than science, and was full of the eloquence of feeling. ing. It occupied one hour and twenty minutes, in the delivery; and the frequent applause which