the outside of these staves, which was painted, continued sound, and that the decay began on the inside, where, from the vats being at different times more of less filled, they were subject to the joint and successive influence of moisture and air.

I have mentioned above, that the putrefactive fermen tation cannot take place except in certain temperatures, the lowest of which, according to Thompson, must be but little below 45 degrees of Fahrenheit's thermometer, and the highest within the degree which produces dryness by evaporation. The temperature most conducive to this effect has not, so far as I know, been ascertained, though much useful information on this head might be obtained from a set of well-conducted experiments.

The following then appears to be the whole theory of the dry-rot; that it is a more or less rapid decomposi tion of the substance of wood, from moisture deposited on it by condensation, to the action of which it is more disposed in certain situations than in others; and that this moisture operates most quickly on wood which most abounds with the saccharine or fermentible principles of the sap. Let us see how this theory corresponds with the best known means of prevention, and what more effectual measures it may suggest.

The first point is certainly to choose timber properly felled and well dried. And here, in order to prevent the injudicious fall of large oak timber, it may be of some consequence to know that the bark of such timber contains much less tan than that of the younger and more succulent wood; and that this principle, together with the proper extractive matter, is considerably more abundant in the bark of the Leicester or Huntingdon willow, than VOL. XIII.-SECOND SERIES.

P

in

in that of any oak. According to the experiments of Mr. Davy, 7 pounds of the former will go as far in tanning leather as 9 or 10lbs. of the latter. It has however been asserted, that if an oak, or any other tree, which is stripped of its bark, be suffered to stand two or three years before it is felled, the wood will have acquired a very great degree of strength and durability.

Next, where it is practicable, a current of air should be frequently made to pass along the surface of the wood. This expedient seems to have been particularly attended to by the ingenious architects of our Gothic churches, who are said with that view to have left various openings in the walls between the two roofs of those edifices. In order also to promote evaporation, a certain degree of heat, such as that of air heated by the sun or fire, should, if possible, be from time to time applied. Cellars themselves ought to have some communication with the outward air by means of windows and shutters, or trap-doors: and that these may be for a short time opened in proper weather, so as to have a draught of air; and that no very low degree of temperature is necessary for the preservation of fermented liquors, provided that temperature be uniform, is evident from the practicability of keeping wine extremely well in cellars which are not damp, and in which, therefore, one or both of these circumstances must have taken place.

The destruction of wainscoating may be long deferred by keeping in the apartment suitable fires.

Lastly, the dry-rot may in all cases be infallibly prevented where it is practicable to cover the surface of the wood, properly dried, with a varnish which is impene

trable

trable and indestructible by water. With this view two or three coats of the composition before described should be laid on the dry wood, before it is erected or put together, and a third or fourth after it is put in its place; and proper means should be taken thoroughly to dry each successive coat of varnish. In situations of this kind, what means of preservation are necessary must be employed at first; as it seems scarcely possible to renew them on fixed timber with any chance of benefit.

I do not know whether in very damp situations, surrounded with stagnant air, these varnishes would in time admit of the growth of fungi or mould. The brimstone might be supposed sufficient to preclude that effect; but, if we believe Braconnot, seeds of the white mustard sown in pure flower of brimstone, and well watered, became vigorous plants, which flowered and produced effective seed. It is certain, however, that the essential oil of turpentine will act as a poison on growing vegetables; and perhaps the same property may exist in resin, which seems to be a similar essential oil, united with a certain proportion of oxygen.

It is however highly probable that the union of the brimstone may have another good effect, which is to prevent one of the causes of the destruction of timber which I have before mentioned, the depredations of insects. Whoever would learn the havoc which certain animals of this kind are capable of making in hot countries, would do well to read Smeathman's description of the Termes, or White Ant, originally published in the Philosophical Transactions, and from thence abridged into the English Encyclopedia Britannica, and other collections. In this country we know little of such ravages.

Mischief however of this kind does sometimes occur,

and may be the work of various animals, a particular account of which may be met with in the fifth volume of the Transactions of the Linnæan Society.

I am informed, that, in India, a circle of Lord Dun donald's coal-tar drawn on the floor round boxes and other furniture, will effectually preserve them and their contents from the depredations of the white ant.

It appears that most insects are fond of sugar and mu cilage; which is the probable reason why that wood is most subject to be penetrated by worms, which is felled when it most abounds with sap. In such cases, it might be well to try the effects of washing the wood, previously to the use of the varnish, with a solution of arsenic in hot water, in the proportion of 1 lb. to 10 gal❤ lons; or with a strong decoction of coloquintida or bitter apple, or white hellebore: after which the wood must be compleatly dried before the application of the varnish in the manner before directed. All these preparations are extremely cheap, and are either destruc tive or offensive to insects, and therefore will, probably, be an effectual defence against any injury from that

cause.

Circus, Sept. 30, 1807.

C. H. PARRY.

On

On the Cultivation of the Poppy.

By T. COGAN, M. D.

From the LETTERS and PAPERS of the BATH and WEST of ENGLAND SOCIETY.

GENTLEMEN,

ALTHOUGH the ardour with which the British nation pursues whatever promises to be of public utility, is perhaps unequalled by any other, and certainly exceeded by none; yet there is one subject which has hitherto been permitted to escape our attention, and in which several nations upon the continent can not only boast of their superior policy, but are already enjoying considerable advantages from it; I mean the cultivation of the poppy to a great extent for the benefit of its oil, as an article of food, and for other useful purposes.

It will doubtless be remarked, that we ought not to ascribe the neglect of it as an article of food to inattention altogether, but to a superior caution, as the narcotic quality of the poppy renders it totally unfit to be taken inwardly. This, it is allowed, is, in appearance, a very formidable objection; and as it respects the lives of multitudes, it ought not to be treated with levity: the objection itself, and the argument from analogy on which it is founded, ought to be completely confuted, before the article can be recommended to the community in this novel point of view.

We might observe that the objection is solely founded upon very slight and imperfect analogy. It assumes that, because some parts of a plant are noxious, the whole must be equally noxious. But this assumption may be confuted in numberless instances.

Daily ex

perience