hal ng tang one sens at each extremity; and the tube is sobaths mi accurate fed not to screw, but to slip down attu the tube of the dyect-glasses, Fig. 1. The lower lens of receives the image from the object-glasses, and this image is examined by means of the upper lens 0. In the focus of the upper lens 0, and lying directly on the plane side of the lower lens O, which is plano-convex, I placed two fine silk threads, crossing each other at right angles. The tube of the eye-piece is sipped down, not screwed down, to its right position in the tube of the object-glasses. It can be turned, therefore, either way freely, without affecting the focal arrangequent of the microscope, which is regulated by other means. And, by turning the eye-piece round, these fine threads, unmagnified, may be applied to the side of any angle of a highly magnified crystal lying on the field below. A brass circle C, about two inches and a half in diameter, with a divided scale on its outer edge, was made to screw fast on to the object-tube T, before the insertion of the eye-piece. And to the edge of the eye-piece a small index I was fixed, so as to lie close on the circle C, and point to the graduate sion. This index is not a simple point, but a vern dicating minutes. To measure the angle of a crystal P the point of the angle to the centre the silk diameters cross each o piece round, to bring one of side of the angle to be p scale at which the index stands. The eye-piece must be again turned till that thread has passed over the whole angle, and coincides with the other side of it. The difference of position of the index read off will give the measurement of the angle. The operation requires some neatness of manipulation, but this is acquired by practice; and if the operation be repeated and a mean taken of the errors which occur each time, it will be easy to come very near the truth. In this way the angles of crystals not more than the four or five millionth of an inch in size may be accurately ascertained. And the introduction of measurement in such cases has surely a great advantage in this respect, that such crystals are more perfect and sharp than almost any that can be obtained of a large size; and that frequently a whole family of crystals, in all their correlative forms and varieties, will be found lying together; such as, in any size adequate for manipulation, the diligent search of a whole lifetime could not have collected. EDINBURGH, 8th April 1835. Description of a New Spring for Shutting a Door, which goes both ways. By ALEXANDER BEATTIE, Foreman to Mr ROBERT RITCHIE, Ironmonger to the King, 241. High Street, Edinburgh.* With a Plate. THE spring is contained in an iron-box, 11 inches by 7, and 11⁄2 inches deep, and consists of two horizontal wheels, marked ose above, and parallel with the door, to which s with the wheels; the levers CC, which move triple springs, EE, are ed or opened to the right nd, drawing back the lever n lever the spring & pr Scotland 11th December 1982. against. There is a cog or stop F on the under wheel, which moves in a groove or slit, cut in the upper wheel, to prevent its being forced too far round. In the same manner, when the lever or door is opened to the left, the upper wheel A is forced round, until it is stopped by the cog F on the under wheel, which pulls round its chain and lever, and is pressed back again by the opposite spring E. In this manner the wheels change the action upon the springs by the door being moved to the right or left. The object of the inventor was to make this spring go into less room and at less expense than the one at present in general use. It has also the advantage of being less liable to go out of order, and can be made to turn more than the quarter circle, which the other cannot. The box may be filled with oil, or the working points oiled occasionally, by removing part of the cover. N. B. By enlarging the diameter of the wheels, and strengthening the other parts in proportion, the spring can be made to suit any size or weight of doors. EDINBURGH, 11th December 1833. Report of Committee of Society of Arts on Mr Beattie's Spring-Door, read 9th April 1834. Immediately subsequent to the meeting at which Mr Beattie's door-spring was exhibited, it was attached to a swing-door, in the premises of one of the reporters, who has paid constant attention to its action, and who, after a trial of three months, is satisfied that, to its other good qualities, it adds that of durabi lity. Your Committee are of opinion that the construction of this door-spring possesses several important advantages over any other they are acquainted with; and as, after a trial of sufficient duration, to have shewn latent defects if it had any which had escaped their notice, they see no reason to alter the favourable pinion they had formed of it, they humbly propose that Mr Beattie should receive some mark of the Society's approbation.* Your Committee beg to suggest that a small alteration should be made in the form of the pieces on which the chains are wound up, which they think should be so proportioned that, as the resistance of the spring increases, the radius to which the chain applies should decrease, and in this way make the resistance of the door equal in every position, instead of, as at present, being greatest when the door is wide open. JOHN ROBISON, Convener. On the different Chronology of the Deluge, according to the Hebrew Text and the Septuagint Translation. In a letter to Professor JAMESON, by Mr JAMES LAURIE, Edinburgh. IN (To the Editor of the Edinburgh Philosophical Journal.) In your last Number, there is an article by Dr Von Schubert, "On the period of the Deluges of Deucalion, Ogyges, and Noah;" wherein the author commits a very palpable error, which, I think, ought to be pointed out. "The calculation of time," says the Doctor, "in the original passage of the Bible, fixes the Deluge in the year 1656, and the Greek translation in the year 2242, after the creation. These two apparently widely different statements agree more nearly than we should at first sight believe. The Septuagint employed a mode of calculating time according to years of 272 days; consequently, to years consisting of ten months, 2242 years of ten months would correspond nearly to 1656 solar years." Now, this statement of Dr Von Schubert proceeds evidently upou the assumption, that the Bible announces in express terms the period of the Deluge. Every reader of the Bible knows that it does no such thing; the dates of the Creation and the Flood being left to be ascertained by a calculation of patriarchal generations, as in the following tables. The first column of * The Society's Silver Medal (value Five Sovereigns) was awarded 12th August 1835. against. There is a cog or stop F on the under wheel, which moves in a groove or slit, cut in the upper wheel, to prevent its being forced too far round. In the same manner, when the lever or door is opened to the left, the upper wheel A is forced round, until it is stopped by the cog F on the under wheel, which pulls round its chain and lever, and is pressed back again by the opposite spring E. In this manner the wheels change the action upon the springs by the door being moved to the right or left. The object of the inventor was to make this spring go into less room and at less expense than the one at present in general use. It has also the advantage of being less liable to go out of order, and can be made to turn more than the quarter circle, which the other cannot. The box may be filled with oil, or the working points oiled occasionally, by removing part of the cover. N. B.-By enlarging the diameter of the wheels, and strengthening the other parts in proportion, the spring can be made to suit any size or weight of doors. EDINBURGH, 11th December 1833. Report of Committee of Society of Arts on Mr Beattie's Spring-Door, read 9th April 1834. Immediately subsequent to the meeting at which Mr Beattie's door spring was exhibited, it was attached to a swing-door, in the premises of one of the reporters, who has paid constant attention to its action, and who, after a trial of three months, is satisfied that, to its other good qualities, it adds that of durabi lity. Your Committee are of opinion that the construction of this door-spring possesses several important advantages over any other they are acquainted with; and as, after a trial of sufficient duration, to have shewn latent defects if it had any which had escaped their notice, they see no reason to alter the favourable opinion they had formed of it, they humbly propose that Mr |