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treated on blights, and so many different theories have been offered to the public, that the subject may appear to many to have been already sufficiently investigated. The society, however, entertained a contrary opinion; and having expressed a wish to receive further information, I avail myself of this opportunity to lay before them some remarks, which I have at different times made during several years of rather close attention to the subject. What are usually termed blights, in the vague and extensive signification of that word, appear to me to originate from three distinct causes : from insects, from parasitical plants, and from unfavourable seasons.

The destructive effects of the aphis on wall trees are so well known, to every gardener, as scarcely to require description. The leaves curl up, the fruits drop off, and the progress of vegetation is almost to tally suspended. Much ill-applied labour is often used by the gardener to destory these insects, though they are not very tenacious of life. Another more extensive, but less fatal disease in plants, the honey dew, is produced by this insect (as described by the abbé Boissier de Sauvages). It has, however, been contended, that the honey dew is not produced by the aphis, but that it is à morbid exudation from the plant; at least, that there are two kinds of it; be cause the leaves are often covered with honey on trees where the aphis is not found, and because the aphis is sometimes found without the honey dew. But to this it may be objected, that honey, not being a volatile substance, will remain on the leaves till it is washed off by the rain; and, when moistened by the dew, will have the appearance

a

of a recent exudation; and that the aphis certainly does not afford honey at any period of its existence. I have frequently placed plates of glass and of tale under the leaves of fruit trees, on which different species of the aphis abounded, and I have found these substances to be in a few hours covered with honey; and I have at other times distinctly seen the honey fall from the under sides of the leaves, where these insect abound, by the following means: Having placed a small branch, con taining a numerous colony of insects, in the window of my study, where the sun shone strongly upon it, I closed the shutters so as to exclude all the light, but that which fell directly on the branch. In this situation the descending drops of honey became extremely visible by refraction, and appeared evidently to be emitted from the insect with considerable force. Each drop contained many minute white points, which I considered as the eggs of the aphis; but, as I knew that the modes of generation in this singular insect had much engaged the attention of naturalists, I did not examine with sufficient attention to decide that point. This species of insect appears to require a previous disposi tion in the tree to receive it; and its first attacks may thence be considered as symptomatic of a previous ill habit in the tree: for I have found that trees which have lately been transplanted, have totally escaped its attacks, when every other tree, of the same kind of fruit, growing in the same situation, has been nearly destroyed. And I can assert, from many experiments, that if every peach and nectarine tree was to be dug up once in every five or six years, and to be replanted with

some

some fresh mould round the roots (which should be as little injured as possible), a much larger quantity of fruit, and of very superior quality, would be obtained. It is unnecessary to inform the experienced gardener, that the tree should be removed early in autumn; that its branches should be considerably retrenched, and that it should not be suffered be bear a heavy crop of fruit in the succeeding season. I have never found any species amongst the numerous and prolific genus of the aphis, which was not readily destroyed on the wall tree by covering it with a sheet of canvas, and under that introducing the smoke of tobacco. It is, however, necessary that the fumigation should be repeated twice or thrice, with intervals of four or five days. I have often seen the addition of sulphur recommended, and have known it tried, but always with fatal consequences to the tree, as well as to the insects.

The blossoms of apple and pear trees are often said, by farmers, to be blighted, when they are destroyed by insects, which breed within them, or in their fruit; and the same term is used, when the leaves have been eaten by the caterpillar: but as the insects themselves, as well as the manner in which their depredations are made, are extremely obvious, they do not properly come under our observation when treating of blights.

The species of parasitical plants which are found in the form of disease on other plants, appear to me greatly to exceed the number of those I have any where seen described by botanical writers. Of these the mildew is the most common and obvious. If a branch, infected with this disease, be struck 2

by the hand in calm dry weather, a quantity of white powder will be found to fly from it; and if this be received on a plate of talc, or of glass, and examined by the microscope, it will be found to consist of very numerous oval bodies, evidently organized. There is another plant similar to this in every thing but colour (being of a tawney brown), which is not unfrequently found on the leaves of young apple trees. Both these plants appear to me to be evidently species of mucor; and as much the greater number of species of this genus of plants is found to flourish in damp air, and in situations deprived of light, it may be supposed that the foregoing diseases might be prevented or removed, by placing the plants at proper distances; but I have not found this to be the case. They, however, abound most in low and sheltered situations; but they are not unfrequently seen in those of an opposite kind. The red and white mould on hops, and the black spots on stalks of wheat (the rubigo of Virgil), and many other diseases of plants, will, I think, be found to arise from the attacks of minute plants of this genus, which appears to me to possess qualities somewhat similar to the digestive powers of animals.

The most common and extensive causes of what are termed blights remain still to be described, and evidently exist in the defects and sudden variations of our unsteady climate. Whatever be the cause by which the sap is raised and propelled to the extremities of trees, it is well known, that its progress is accelerated by heat, and that it is checked, or totally suspended, by cold; and it has been ascertained by others, as well as by myself, and indeed is

known

known to every experienced gardener, that a plant under the most skilful management, does not readily recover its former vigour, when it has been injured by exposure, for a few hours, to a temperature much below that to which it has been previously accustomed. It frequently happens in this climate, when the blossoms of our fruit trees are just expanding, that a very warm day succeeds a night whose temperature has been some degrees below the freezing point of water. In such a day the evaporation from the unfolding leaves and blossoms will be greatly increased by the agency of heat and light, whilst the supply of nourishment is in a great measure cut off by the ill effects of the preceding night. The blossoms will nevertheless unfold themselves, but will be unproductive, from the want of due nourishment; whilst the hazy appearance of the air, which almost always accompanies such weather in the spring, will induce the gardener unjustly to infer that the ill effects he observes have arisen from some quality in the air (distinct from excess of heat and cold), which he denominates a blight.

The best defence against this kind of weather for wall trees, that I believe has yet been tried, is a covering of a double and triple net; for by this the tree is in some degree protected from frost; and the excess of evaporation, in the succeeding day, is in a very considerable degree prevented. Lightning is supposed by many to be very highly injurious to the blossoms of trees; but I believe that the ill effects which appear sometimes to accompany it may be more justly attributed to excessive heat. The careful gardener often covers his trees with mats, or

something of this kind; and by almost totally depriving the trees of light, creates that blight which he is anxious to exclude.

As the blossoms of every tree are formed during the preceding summer and autumn, they will evidently be more perfect in proportion as those seasons have been favourable, and as the management of the gardener has been judicious; and as the power of bearing unfavourable weather will be proportional to their vigour, and to the maturity of the annual wood, through which the sap passes to support them, the gar dener should be (though he rarely is) extremely attentive to keep his trees in such a state, and the branches at such distances from each other, that they may receive the greatest possible benefit from the portion of light and heat which our shadowy climate affords them. It frequently happens in pruning, that too much bearing wood is left on the tree. Every gardener ought to know, that where a hundred fruits are a sufficient crop for a tree, he has a better chance to obtain that hundred from one thousand blossoms, to which the whole nourishment of the tree is directed, than when the same quantity of nourishment has to support a hundred thousand.

In standard fruit trees, where no advantages can be derived from covering them, much may be done by the judicious application of the pruning knife. The branches of a tres of this kind ought to be much thinned towards their extremities, so that the light may be admitted into the centre of the tree; but the internal parts of it should never be so thin as to admit of a free current of air through it. When a tree has been properly pruned, blossoms and

fruit will be found on every part of it; and, in unseasonable seasons, the internal blossoms will receive protection from the external branches, which will be unfruitful.

It is particularly the interest of every planter, to take care that the varieties of fruit which he plants be sufficiently hardy for the situation in which he places them; for if this be not attended to, little benefit will be derived from the foregoing observations.

Method of preserving fresh Water sweet during long Voyages. By Samuel Bentham, Esq. of Queen's square, Westminster. From the Transactions of the Society for the Encouragement of Arts, Manufactures, and Commerce.

HE mode in which I conceived

Tfresh water might be preserved

sweet, was merely by keeping it in vessels of which the interior lining at least should be of such a substance as should not be acted upon by the water, so as to become a cause of contamination. Accordingly, on board two ships, the greater part of the water was kept, not in casks, but in cases or tanks, which, though they were made of wood, on account of strength, were lined with metallic plates, of the kind manufactured by Mr. Charles Wyatt, of Bridge-street, under the denomination of tinned copper-sheets; and the junctures of the plates or sheets were soldered together, so that the lightness of the cases depended entirely on the lining, the water having no where access to the wood. The shape of these cases was adapted to that of the hold of the ship, some of them being made to fit close under the

VOL. XLIV.

platform, by which means the quantity of water stowed was considerably greater than could have been stowed, in the same space, by means of casks; and thereby the stowageroom on board ship was very much increased.

The quantity of water kept in this manner on board each ship, was about forty tons, divided into sixteen tanks; and there was likewise, on board each of the ships, about thirty tons stowed in casks as usual.

As the stowing the water in tanks was considered as an experiment, the water in the casks was used in preference; that in the tanks being reserved for occasions of necessity, excepting that a small quantity of it was used occasionally for the purpose of ascertaining its purity, or

when the water in the casks was deemed, when compared with that in tanks, too bad for use.

The water in thirteen of the tanks, on board one ship, and in all the tanks on board the other, was always as sweet as when first taken from the source; but in the other three of the tanks, on board one ship, the water was found to be more or less tainted as in the casks. This difference, however, is easily accounted for, by supposing that the water of these tanks was contaminated before it was put into them; for, in fact, the whole of the water was brought on board in casks, for the purpose of filling the tanks, and no particular care was taken to taste the water at the time of taking it on board.

After the water kept in this manner had remained on board a length of time, which was deemed sufficient for experiment, it was used out, and the tanks were replenished as occasion required: but in some

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of the tanks, on board one ship at least, the original water had remained three years and a half, as appears by the certificates herewith enclosed. About twenty-five gallons of the water, which had remained this length of time in the ship, are sent to the society, in two vessels made of the same sort of tinned copper with which the tanks were lined.

A certificate from captain Wm. Bolton, commander of the said vessel, dated Sheerness, 28th of June 1800, accompanied this letter, stating that the water delivered to the society was taken from a tank holding about 700 gallons, and which his predecessor, captain Portlock, had informed him had been poured into the tank in December 1790, except about thirty gallous added in 1798, and had remained good during. the whole time.

The signatures to the above accounts were certified, on the 23th of June 1800, by the rev. C. Thee, minister of Sheerness.

In a letter, dated January 27, general Bentham also states, that the water which had been preserved sweet on board his majesty's sloops Arrow and Dart, and of which he had sent specimens to the society, was taken from the well of the king's brewhouse at Weevil, from whence ships of war, lying at or near Portsmouth, are usually supplied with water for their sea-store, as well as for present use.

Account of a Diving Boat.

geur, a diving boat, lately discovered by Mr. Fulton, an American:

"I have," says he, "just been to inspect the plan and section of a nautilus, or diving boat, invented by Mr. Fulton, similar to that with which he lately made his curious and interesting experiment at Havre and Brest.

"The diving boat, in the construction of which he is now employed, will be capacious enough to contain eight men, and provisions enough for twenty days, and will be of sufficient strength and power to enable him to plunge 100 feet under water, if necessary. He has contrived a reservoir for air, which will enable eight men to remain under water for eight hours. When the boat is above water, it has two sails, and looks just like a common boat. When she is to dive, the masts and sails are struck.

"In making his experiments at Havre, Mr. Fulton not only remained a whole hour under water with three of his companions, but kept his boat parallel to the horizon at any given depth. He proved that the compass points as correctly under water as on the surface, and that while under water, the boat made way at the rate of half a league an hour, by means contrived for that purpose.

"It is not twenty years since all Europe was astonished at the first ascension of men in balloons: perhaps in a few years they will not be less surprised to see a flotilla of diving boats, which, on a given signal, shall, to avoid the pursuit of an enemy, plunge under water, and rise again several leagues from the place

CITIZEN f
NITIZEN St. Aubin, a man of

of the tribunate, has given the fol-
lowing account of the lateau plon-

"The invention of balloons has hitherto been of no advantage, be

cause

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