portionate to the degree of obliquity with which it strikes upon the surface of the glass; and it is therefore important to every builder of a Forcing House to know by what elevation of the roof, the greatest quantity of light can be made to pass through it. To ascertain this point, I have made many experiments, and the result of them has satisfied me that, in latitude 52, the best elevation is about that of 34 degrees and relative to that elevation the position of the sun, in different parts of the year, will be nearly as represented in the annexed sketch, which is taken from the Vinery I have mentioned. About the middle of May, the elevation of the sun will nearly correspond with that of the asterisk A (Fig. 6. Plate IV.), and in the beginning of June, and again early in July, it will be vertical at B, and at Midsummer it will at C be only 6 degrees from being vertical. The asterisk D points out its position at the equinoxes, and E its position in midwinter.

In this building, which is forty feet long, and is heated by a single fire-place, the flue goes entirely round without touching the walls; and in the front a space of two feet is left between the flue and the wall, in the middle of which space the vines, which are trained to the roofs, about eleven inches from the glass, are planted; and as both the wall and flue are placed on arches, the Vines are enabled to extend their roots in every direction, whilst, in the spring, their growth is greatly excited by the heat, which their roots and stems receive from the flue. Air is generally admitted at the ends only, where all the sashes are made to slide, to afford a free passage of air through the house, when necessary, to prevent the Grapes becoming mouldy in damp seasons. About four feet of the upper end of every 3d light of the roof, is made to lift up, (being attached by hinges to the wood

wood-work on the top of the back-wall) to give air in the event of very hot and calm weather; for I prefer giving air by lifting up the lights, to letting them slide down, because when the former method is adopted, no additional shade is thrown on the plants.

The preceding plan is here particularly recommended for a Vinery only; but I am confident that by sinking the front wall below the level of the ground, and making a small change in the form of the bark-bed, the same elevation of roof may be made equally applicable to the pine stove, and that no upright front glass ought, in any case whatever, to be used; for light can always be more beneficially admitted by adding to the length of the roof, if that be properly elevated; and much expense may be saved both in the building, and in fuel. For forcing the Peach or Nectarine, I must, however, observe that I think any house of the preceding dimensions wholly improper; and I purpose to submit a plan for the improved culture of those fruits to the Horticultural Society at a future opportunity.

The Vine often bleeds excessively when pruned in an improper season, or when accidentally wounded, and I believe no mode of stopping the flow of the sap is at present known to gardeners. I therefore mention the following, which I discovered many years ago, and have always practised with success: if to four parts of scraped Cheese be added one part of calcined Oyster-shells, or other pure calcareous earth, and this composition be pressed strongly into the pores of the wood, the sap will instantly cease to flow; the largest branch may of course be taken off at any season with safety.

Application

Application of the Heat (that escapes through Chimneys of the Boilers in large Establishments,) to a Ventilator and a Stove, which may be adapted to the Fabrication of Syrups, Sugar, Soap, and Indigo; to the Manufacture of sulphuric Acid, raw Soda, and Salt of Soda, of Alums Potash, and Salt-petre, and all others where Liquids are evaporated, and the extracted Matter dried.

By M. C. PAJOT DES CHARMES.

(Continued from Page 60.)

IN order to give a view of the advantages depending on this evaporator, submitted to the ventilation produced by the heat in the chimney, it is sufficient to say, 1st, that the result of the cold experiment, made over a vessel of eight feet by four, and containing eight inches of liquid, as in the preceding experiments, gave in twenty-four hours an evaporation of a nineteenth part of the mass; 2d. that the same quantity of liquid evaporated by the same means, in the same vessel, heated only at the bottom, was reduced one-twelfth part during the same pe riod of twenty-four hours. The temperature of the liquid in the second instance was not raised beyond 60 degrees of Reaumur.

By adopting, therefore, in the front of a set of evaporators to be heated, a similar set of cold evaporators, it is easy to reckon before hand, at least by approximation, the advantages attached to this combination. Thus, by following the process of cold evaporation, a previous concentration of the liquid will be obtained, which, when poured into the warm evaporators, disposed in the same manner as the cold, will yield its product in a space of time necessarily very short, compared with the time required by the ordinary methods.

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To this economy of time, which is the most precious, as it at the same time saves both fuel and labour, is added the advantages resulting from the application of the cover upon the boilers, and which consist in the cleanliness and salubrity of the establishment, circumstances which have the greatest influence on the quality of the product.

The aperture made in the chimney should not be done indifferently; that which has given place to the ventilator was stopped according to the knowledge of the degree of heat of the body of the chimney on the outside, its thickness being always taken into consideration. In the application now in question, the aperture in the chimney was made twelve feet below the fire-place of the reduce?, which was the mean height between the fire-place and the upper extremity of the chimney above the roof. One of Reaumur's thermometers put in this place, and in contact with the wall of the chimney, which was eight inches thick, indicated 80 degrees.

The aspirating aperture on the side of the cold evaporators built against the opposite front of the body of the chimney was made three feet above the air-hole on the side of the warm evaporators. At these different elevations the play of these two species of aspirating pumps occasions no risk of accidental fire either to the building or the covers, which, by way of precaution, were coated with a light coat of plaister, in the length of from two to three feet from their base.

It will be observed, that the rarifying force of the beat that escapes naturally determines the velocity of the air that is drawn under the case and cover of the boilers. The product of the vaporisation follows in proportion.

Although the doors or flaps in the case that were made to open at the side of the boilers have been described as turning on hinges, they may nevertheless be made to slide; VOL. XXV.-SECOND SERIES.

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or,

or, perhaps, Venetian-blinds would be still more advan tageous from the facility they would afford to the distribution of the current of air in the most convenient way for the evaporation of the liquid.

I have tried at different times the effect of opening the doors which touch the body of the chimney at the same time with those placed above the fire-places: I thought that the common action of the two currents of air intro→ duced at once would produce a more considerable evaporation, but my expectations were deceived, for the air, in passing along the wall of the chimney, appears to injure the celerity of that which comes in the line of the fire-place.

It is not useless to note, that the ordinary temperature of the building, where the set of warm evaporators were disposed, was from 15 to 20 degrees of Reaumur, and that observed in the opposite part where the cold evapo rators were placed was nearly 25 degrees. This latter temperature was produced by the heat transmitted through the body of the chimney, and more subject to a concentration in the second locality as it was much less spacious than the first.

I ought to observe, that when the salt is intended to be extracted in a crystalline form, the vessel into which it drops should be removed, in order that it may not be in the way of the evaporator belonging to the reducer.

This instrument has been employed, constructed in two ways: the first model was composed of a wooden frame, in the shape of a hammer; at each end of its cross piece were fixed small wheels, or pullies; either a single one, with shoulder piece and sockets, or two toge

ther;