This agreement is no doubt very remarkable, and the more so, as, in comparing stationary with insulated observations, we confound the mean state of the atmosphere in the course of a whole year with the decrease which corresponds to a particular season, or a particular hour of the day. M. Gay-Lussac found, in his celebrated aëronautical voyage from 0 to 7000 metres, (0 to 22,960 feet), a centigrade degree for 187 metres, near Paris, at a period when the heat of the plains was nearly equal to that of the equinoctial region. It is on account of this observed equality in the decrease of heat, in reckoning from the standard temperature of the plains, that the astronomical refractions corresponding to angles below 10°, have been found the same under the equator and in temperate climates. This result, contrary to the theory of Bouguer, is confirmed by observations which I have made in South America, and by those of Maskelyne at Barbadoes, calculated by M. Oltmanns.

We have seen, that between the tropics, on the back of the Cordilleras, we find, at 2000 metres of elevation, I will not say the climate, but the mean temperature of Calabria and of Sicily. In our temperate zone, in 46° of Lat. we meet at the same elevation with the mean temperature of Lapland†. This comparison

temperature of October is even a little below that of the whole year, it is probable that the height of the plain of Great Thibet exceeds from 2900 to 3000 metres.See my Memoir on the Mountains of India in the Ann. de Chim. et de Phys. 1817.

Note by the Editor.

As the cold meridian of the globe passes through the plains of Great Thibet, we conceive that the mean temperature of Lat. 29° in that plain, when reduced to the level of the sea, will be about 65°, and therefore that the height of the plain of Great Thibet will not exceed 2800 metres or 9184 feet.-D. B.

• Saussure gives for the summer 160 metres, (525 feet); for winter 230, (754 feet); and for the whole year 195, (640 feet). M. Ramond gives 165, (538 feet). M. D'Aubuisson 173 metres, (567 feet).-See Journ. de Phys. tom. lxxi. p. 37.; De la Formul. Barometr. p. 189.; and my Recueil d'Obs. Astron. tom. i. p. 129.

+ As the temperature varies very little in the course of a whole year in the equinoctial zone, we may form a pretty correct idea of the climate of the Cordil

leads us to an exact knowledge of the numerical ratios between the elevations and the latitudes, ratios which we find indicated with little precision in works on physical geography.

The following are the results which I have obtained from exact data in the temperate zone, from the plains to 1000 metres of elevation. Every hundred metres of perpendicular height, diminishes the mean temperature of the year, by the same quantity that a change of 1° of latitude does in advancing towards the Pole. If we compare only the mean temperature of summer, the first 1000 metres are equivalent to 0°.81 Fahr. From 40° to 50° of latitude, the mean heat of the plains in Europe decreases in Europe 12°.6 of Fahr.; and this same decrease of temperature takes place on the declivity of the Swiss Alps from 0 to 1000 metres of elevation.

b. At an elevation of 1000 metres, 41.00 58.46 42.80

These numerical ratios are deduced from observations made on the temperature of the air. We cannot measure the quantity of heat produced by the solar rays on the parenchyma of plants, or in the interior of fruits which receive their colour in ripening. The fine experiment of MM. Gay-Lussac and Thenard, the combustion of chlorine and hydrogen, proves what a powerful action direct light exercises on the molecules of bodies. But as the extinction of light is less upon the mountains in dry and rarified air, maize, fruit-trees, and the vine, still flourish at heights which, according to our thermometrical observations. made in the air, and far from the ground, we ought to suppose

leras, by comparing them to the temperature of certain months in France or in Italy. We find in the plains of Orinoco the month of August of Rome; at Popayan, (2988 feet), the month of August of Paris; at Quito (4894 feet), the month of May; in the Paramos, (5904 feet), the month of March at Paris.

too cold for the cultivation of plants useful to man. M. De Candolle, indeed, to whom the geography of vegetables owes so many valuable observations, has seen the vine cultivated in the south of France at 800 metres (2624 feet) of absolute height, when, under the same meridian, this same cultivation went on with difficulty at 4° of latitude farther north; so that if we consider only the ratios in France, an elevation of 100 metres, (328 feet), appears to correspond, not to 1°, but to half a degree of latitude*.

(To be concluded in next Number.)

ART. VII.-Description of a Machine for Raising Stones. By DAVID LOW, Esq. †

THE curious machine to be now described, has been employed in some places for the purpose of clearing uncultivated ground of such large masses of granite or whinstone, as could not be moved but by the aid of gunpowder. It is, I believe, very little known; and yet, as an useful instrument, it well deserves attention. As it affords, besides, the means of making a very singular philosophical experiment, I trust that a page or two of the Edinburgh Philosophical Journal may be well employed in disseminating a knowledge of its properties and construction. With this view, I shall endeavour to describe a convenient form in which it can be made for practical uses, and the purposes of experiment.

In Plate VI. Fig 1. A, B and C represent three strong wooden posts, about 14 feet in length, through the ends of which

See my Prolegomena de Distributione Plantarum, p. 151. 163. The small differences between the numbers given in the Prolegomena and in this Memoir, written subsequently, should be ascribed to the constant desire which I have had to perfect the mean results.

This machine was invented by Mr Richardson of Keswick, who was rewarded for the invention by the Society of Arts. We have not heard of its having been used to any extent in England, but in Scotland it has met with high approbation wherever it has been employed, though we believe it is but little known among that class to whom it is likely to be of the greatest utility.-D. B.

are three holes abc, for the reception of the strong iron pin, DE, upon which is made to slide the curved ironbar CG. The pin is so thrust through the holes in the posts already mentioned, that the post C of Fig. 1. shall be next to the thick end of the pin E; the post B in the middle at b, within the bend of the crooked bar CG, and the post A next to the pin at D, which is thrust through the other to keep the apparatus together. The holes a be being of such a size as to allow a little play to the posts, these last may be stretched out like the legs of the common theodolite, in the manner represented in Fig. 1. To the curved iron-bar are then attached the fixed block M, containing four or more pulleys, and the moveable block N, containing the like number of pulleys. Each of these blocks must be hooped with a very strong bar of iron, and the pulleys must be of a size to admit of a thick rope passing over them. To the lower block N is to be hooked the iron plug P, consisting of a ring, a flat part, and a cylinder. The cylindrical part may be 7-8ths of an inch in diameter at the point, gradually increasing to about the 16th part of an inch more in diameter at the neck, and being about 2 inches in length. The end of the rope O, in Fig. 1. passing over the fixed pulleys, is attached to the windlass FH, which may be 6 feet or more in length, and which is fixed by its axis to the posts A and C. At each end of this windlass is a winch T and U, for the purpose of saving time, by tightening the ropes previous to the windlass being worked. The windlass is worked in the usual manner, by levers, for the reception of which are mortises, as shown in the figure. At one end of the windlass is fixed the ratchet wheel VY, (the catch X being fixed to the post A,) for the purpose of preventing the weight from falling back when the moving power is withdrawn. The two posts A and C should be connected by a cross bar, to keep them steady in their place.

The machine thus described is easily managed. It is placed over the stone to be raised, by extending the posts on each side, and then the windlass is attached. Of the stone to be thus raised, however large it be, it is enough to see the smallest part appear above the surface of the ground. At this part let a workman, with a mallet, and the common steel-boring chisel of ma

sons, make a small circular hole, about two inches deep, and as perpendicular as possible. This chisel should be of such a size as to make the hole about a sixteenth part of an inch less in diameter than the plug itself, so that a stroke or two of a hammer may be necessary to drive the iron home. When the latter is thus driven an inch, more or less, into the stone, it is attached to the block, and the ropes are tightened by turning the winch. Nothing more is now requisite, than to set as many persons as may be required to work the windlass; and, strange as it will seem, with no other fastening than this simple plug, the heaviest mass will be torn up through every opposing obstacle, and lifted into the air.

I could well pardon incredulity in any one who was, for the first time, told of such an effect produced by such means. When the fact was mentioned to some distinguished men of science in this country, they remained incredulous, and were only convin ced by seeing the engine itself at work; and I have not heard that any of these gentlemen have explained the principle of action of the machine. I understand that the general opinion, on first witnessing the experiment, was, that the iron-plug, when driven into the stone, was not precisely in the direction of the moving power, and that the mass was raised and suspended in the manner shown by the plugs A and B, in Fig. 2. This explanation, I apprehend, cannot be admitted; and it is to the elasticity of the stone, and not to the direction of the moving force, that we must attribute the effect produced. The iron is forced down by a stroke, and retained in its position by the elastic power of the stone, in the same manner as a similar pin would be held by a block of wood, into which it was forced by the same means, with this difference, that the elastic power exerted upon the iron by the harder stones, would be incomparably greater than that exerted by the wood. That this is the true explanation of the phenomenon, is confirmed by the facts of the experiment itself: For, 1st, It is found, that the moving power may be made to act in the direction of the hole with the utmost precision, without varying in the least the result; 2d, That when the mass is raised from the earth, it may be moved into any position without being detached; and, 3d, That, while hardly any constant force will pull out the plug, a smart