Sir,-In answer to the inquiry of "Litera," in your 690th Number, I beg to suggest the following method of procuring several copies of a letter with expedition and secrecy :

First write the letter with a pen on a sheet of paper (even as I am now doing), but instead of ink, employ the greasy or soapy substance well known to those who dabble in lithography, wetted with water, and which looks like a stick of Indian ink folded up in a thin sheet of lead. Then lay the letter fresh written on the face of a lithographic stone, and submit it to high-pressure for a short time; and the characters will be vividly transferred. (If the letter were held for a moment over steam to damp it, the better success of the transfer would be promoted.) Lastly, wet the stone, and print forthwith. All this might be accomplished by one person "in secret," in as little

time as it has taken me to write this letter.

Yours obediently,

F. O. H. SIDMOUTH ENSIS.

London, Nov. 1, 1836.

MODE OF PRESERVING THE GAS OF BALLOONS-CARBONIC ACID FOR BALLAST.

Sir,It is gratifying to know that an active movement is, at last, being made for turning to some useful purpose a discovery which has for so long a period been a matter more of idle curiosity than otherwise. The papers on that subject which have from time to time appeared in your excellent Magazine, will form au interesting feature in the history of aeronautics; and it is hoped that these will be continued, notwithstanding the chapters of " improbabilities" which, on the whole, have not as yet put forth any plausible objection to the purpose.

Considering the great expense which

attends the inflating of a balloon with coal-gas, owing to the unusual charge made by Gas Companies on such occa sions, it would be desirable that some means were devised whereby the volume of gas might be turned to better account than heretofore. At present a large quan tity is thrown away in order to cause the descent of the bailoon, and the residue is as freely parted with when it has descended. Now, if two or more "ascents" could be made conveniently with the same volume of gas, and at the expense of one ascent, it is not unlikely that the so doing would be accounted an improvement. The following inethod is simple-1st. Let a spherical, air-proof, silk bag be suspended from a hoop tra versing the circumference of the balloon near the top, reach within a few feet from the neck, and be connected to the apparatus, afterwards described, by an airproof tube passing through the neck of the balloon; this bag to be the recepta cle for carbonic acid gas, to be generated when the machine is required to descend. 2d. Let a small cask, 12 or 14 inches wide, be fastened beneath the car; this cask to be equally divided by a cross partition, having an aperture in the centre provided with a leaden plug, fitting closely, and raised by a wire passing through the tap; each division to have an opening for introducing substances, and the lower one an additional orifice, into which is inserted the conducting tube to the silk bag. Such an apparatus would not be obstructive, nor its weight considerable; the cask, suitably deco, rated, might be fixed under the car, and the tube be placed along one of the cords suspending the car.

Now, supposing that a balloon has gained a high elevation, it is necessary, in order to cause its descent, that the ascending power be overcome. To attain this end by means of the apparatus above described, it is necessary while inflating the balloon that a space be left as allowance for the distension of the ballast-bag. Now, let the stopper in the cask be raised, instantly the dilute acid will act upon the chalk, and the dense gas discharged thereby will rush with rapidity along the tube and expand the bag; the latter, by its weight, will in a short time produce the desired effect; the supply from the cask may easily be regulated and checked when necessary

Sir, We have endeavoured to trace a relation between the structure and functions of plants, and the properties of the surrounding elements, favouring the conelusion that electricity is the grand agent by which the several processes of vegetation are carried forward. Air, water, and solar light, have respectively been viewed as conveying electric influence to the vegetable kingdom. The predominant influence of each of these elements appears to take place in the order just mentioned; and the dry winds of March, the copious rains of April, and bright sunshine of May, appear to exhibit this succession in a general view, while the mingled and varying states of the weather show the almost continual necessity of their mingled operation in different degrees. It may here be observed by the way, that whereas the vital principle in animals is maintained by means of a portion of the atmosphere which is uniformly supplied at all seasons, and is administered to all the more perfect kinds in the exact proportion which is requisite to preserve the uniformity of their heat and vitality; that of vegetables, depending on the vicissitudes of the seasons, and even on the variations of the weather, is subject to the like vicissitudes and variations. To me it appears, that in reality they both depend upon the same, subtile fluid as emanating from the sun; out whereas, plants derive it in an uncombined state from the floating winds, the condensing vapours, and the direct rays of the sun; animals imbibe it by means of the peculiar organisation of the lungs in those more copious and uniform supplies which their more elevated nature requires, by a chemical decomposition of oxygen in those organs. But

this important branch of inquiry cannot be pursued in this place. I now wish to offer a few remarks on the progress of vegetation under the influence of the several elements.

1st. The electric influence of the air in producing the first excitement and spring of vegetation, appears to depend much on the partial absence of its influences under the forms of condensing vapour, and of solar light; as these, by employing the electric fluid in the processes of growth and maturation, would direct large quantities of it from that which is all-essential in the first instance. Hence, our March commences with a total destitution of leaves in all the more foliagenous species of trees, while the annuals among herbs have disappeared. The only vegetative remains of these respective kinds are contained in the buds protruding from the trees, and the seeds which lie concealed in the soil. Thus a large proportion of those rays, which, as the season advances, are employed in the two subsequent processes of vegetation, are reserved to impart electricity to the air, as the instrument of producing the first excitement in the yet closed germs. As a farther preparation,—during the winter now at its termination, the vapours exhaled into the atmosphere in the preceding summer are gradually condensed, and conveyed into the earth in the forms of rain, snow, and hail, by which means that extraordinary dryness, which distinguishes the early spring, and is remarked by agriculturists for its salutary effects, is in part produced; and in part, probably, by the rarifying influence of the increasing rays, causing the lower strata of our climate to ascend and give place to the denser and yet drier air rush-* ing in from regions into which fewer vapours had been exhaled, and from which they had been more completely removed by a more condensing temperature. These winds are, moreover, of use in removing all particles of moisture, together with other impurities from the exterior of plants, and from the surface of the soil; so that nothing may be left to be acted upon by the electric influence, but the buds, seeds, and emerging shoots. When the winds have sufficiently per formed their office of desiccation, that of vegetative excitement and germination seems speedily to commence. The glancing rays of the early season of the year

are evidently more favourable to their accumulation in the atmosphere than the more direct rays of the advancing season; and from this cause, in conjunction with those above stated, a much larger proportion of them will be lodged in the air, or resting upon it, reaching to some distance upward, than at a later season. The electric matter accumulating in the higher strata will propel it downward, and probably at once force a portion of it. into the earth, and cause a partial state of negation of it upon its surface; which being followed by a powerful rush upward, as the temperature and rarefaction of the contiguous air increases, must give a great impulse to the seeds and shoots, and act as the immediate cause of germination. As the first incitement to the seeds contained in the soil may thus be produced, so that of the buds of trees must be greatly promoted by the electricity of the rushing winds.

That the electricity is much more intense during the cold, dry winds of March in a clear atmosphere than at any other season, I have been assured by Mr. Sturgeon to be the result of his numerous experiments, in conformity with the few observations which I have made. It may be worth while, however, to observe, that the conclusion had presented itself from the above considerations previously to his favouring me with this information; so that theory and experiment have in this respect coincided, without the one being biassed by the other. That a negative state of the seed and the soil in which it is deposited, in respect to the atmosphere, is peculiarly favourable to germination, while it is much promoted by electricity in general, appears from the following experiment. I sowed some mustard-seed on the 20th April in similar soils, one electrified positively, a second negatively, and a third in its ordinary state. days the electrified plants appeared, but those negatively electrified were the most advanced; those not electrified did not appear till two days later. On the 12th May the plants, in a negative state, had grown to 2 inches; those in a positive state to 24 inches; those not electrified to 1 inches; the electrified plants were strong and flourishing in proportion. The superiority of negative over positive electricity in the seeds, and of either in promoting their vegetation over seeds in the ordinary state, had been observed and

In four

supported by numerous experiments by Dr. Caxmoy and the Abbé d'Ormoy, many years since, though I had no expectation of such a result at the time of making the experiment, prior to my remarks on the relative electricity of the atmosphere and the soil. It is probable that any state of electricity, by propelling the fluids of vegetation, causes expansion and growth; while that which acts in an upward direction, like that of the atmosphere upon the soil, is most efficacious. Mr. Weekes confirms the general fact in its application to positive electricity, by observing, that his " electrified plants appeared several days before others," placed with a rigid regard to the sameness of circumstances, excepting the absence of electricity; and that "they continued afterwards to grow with a much greater degree of vigour." has also produced similar results by means of the galvanic battery, with the particulars of which, as of many other experiments on vegetation, "especially with plants growing at various altitudes," which I have reason to conclude he has been pursuing with ardour during the last summer, I trust he will ere long favour the public.

He

I am here induced to recite the particulars which I received from a medical electrician, of which a general mention has been made. A narcissus plant which was in a very languishing state, being placed in the room in which his powerful electric machine was kept in frequent action, soon began to exhibit signs of extraordinary vigour. It grew to the height of thirty-six inches, and was stout Some and luxuriant in proportion. branches of the moss-rose and various other flowers placed in water on the mantle of his room, retained their colours while the seeds were forming, during about five weeks, and at last dropped off without assuming a withered appearance. A hawk's-cap lily drooped during several hours of the night when the action of the machine was suspended, but resumed its vigour, and again stood erect under its renewed action. These particulars, on the general correctness of which I have every reason to rely, are admirably illustrative of the principle, that a relative state of negation in the source of vegetation from beneath, as compared with the positive state of the atmosphere, though without any absolute addition to the

quantity of electric matter, is a most material requisite to its origin and progress. The general high temperature of the room no doubt aided considerably in the process. I lately observed that, whereas sprigs of plants inserted in water, from which the carbonic acid has been expelled by boiling, appear to perish nearly as rapidly as if they had been destitute of moisture, when the water is impregnated with an additional quantity of this gas they retain their vigour; which agrees with a similar experiment on the autumnal leaf above related, by which its drop, without withering on the branches, appears to been owing to the presence of carbonic acid in the water. It appears, therefore, highly probable that this gas is essential, or greatly conducive to the rise of the sap in consequence of the affinity of its oxygen with the positive electricity of the atmosphere, while its carbon is separated from it and deposited in the leaf, or conveyed into the substance of the plant. In consonance with this position, Mr. Weekes, in a letter of May 14th last, has the following interesting statement:-"As far as my experiments have yet gone, I am justified in saying that carbonic acid appears to be most abundant about the end of the spring months and the beginning of summer; it decreases gradually (leaving out of consideration contingencies from local causes), and, of course, its quantity is least in the ordinary atmo. sphere during the months of winter."

The electricity of the air, as distin guished from that of vapours and of solar light, has chiefly occupied the above remarks. My endeavour has been to show that the solar fluid is economised in it, to the exclusion, in a great degree, of the action of vapours and of the direct rays of light upon the shooting and expanding leaf, for the purpose of imparting the first excitement to the germ. The process of nutrition, in connexion with an increased supply of electric matter, as the principle of vitality now becomes indispensable, and is accordingly administered in abundance.

I must postpone the additional remarks which I wish to offer on the latter processes of vegetation to a subsequent occasion, should the further prosecution of the subject prove acceptable to your readers. It was my design to have com

pleted my view of electro-vegetation in a less interrupted series; but besides that, other engagements have occupied much of my time-particularly in connex ion with a Mechanics' Institution recently formed in this town, and. I have the pleasure to say, with a success in point of numbers, unanimity, and activity, and under the auspices of a reformed corporation, which affords every indication of extensive usefulness-I find so many dif ficulties to encounter, with some new lights occasionally breaking in upon the wide field into which I have adventured with my able coadjutor, that I am often obliged to suspend farther remarks for more mature and satisfactory information. I owe to several of your correspondents my respectful acknowledgments for the very favourable notice which they have taken of my letters; particularly a gen. tleman under the signature of W. B., in your Number of May 14th last, in connexion with his remarks upon the theory of Mr. Mackintosh, and, I think also, Mr. Mackintosh himself in a recent Number. As the statement of his theory con tained in your No. 645, December 19th last, is now before me, I cannot abstain from offering a remark or two with relation to it; but it must be chiefly to notice the ground-work upon which it proceeds. I allude principally to his account of the Franklinean theory, which in several particulars is incorrect, as stated by Franklin himself, and as may be easily proved by a few of his plainest and most decisive experiments. But, notwithstanding the inaccuracy, particularly of the assertion that non-conductors contain very small portions of electricity, or, as I prefer terming-it, electric fluid, I am not aware that Mr. Mackintosh's theory is materially influenced by it, which, from the cursory attention I have hitherto given it, promises, I should think, to throw considerable light on the future researches of philosophy. In short, the observation of your correspondent, Ursa Major, that " it is drawn up with muchingenuity; that there is an air of proha-d bility, and in some parts even of plausi bility, about it, which renders it emi-bas nently worthy of investigation shy otheiw scientific world," is in unison with my goo own convictions; at the same time that Iftiw cannot help strongly concurring in what s the same writer adds with respect to the ad wise authorship and superintendenced of 209

the Ruler of the Universe. Indeed, as human experience has uniformly witnessed nothing but the most complete control over the powers of nature, so that what would otherwise prove most destructive, is so overruled and regulated by counteracting causes, as to produce the most harmonious and beneficial effects, its analogies furnish strong grounds on which to repose our reliance for the future; and that any tendencies to evi! which may hereafter lead to its actual production, will in due time meet, in like manner, with counteracting causes productive of the like salutary issues. If discoveries in astronomy, geology,

&c. have shown that disorders have occasionally occurred; that our globe has been converted into a chaos, and that other globes or systems have disappeared from the universe; the actual state of things abundantly manifests something more than that these disorders have not been suffered to continue; the present state of our globe, with its principal inhabitant, of an order greatly superior to any of which traces remain in its former states, evinces that the evil has given occasion to a predominance of good, while the general harmony of the mundane universe shows that no even apparent evils have been suffered to have a permanent continuance.

In your Magazine, No. 639, p. 101, &c. I have alleged some facts in proof of the position that there is one uniform fluid issuing from the sun as its principal source and centre, which, under different circumstances, produces the several phenomena to which the terms light, heat, or caloric, and electricity, are applied. It is to me perfectly evident, that the stream of light which may be seen issuing from the mercury of a thermometer into the vacuum above, on applying positive electricity to the ball, is a real fluid. This fluid, instead of being contained in small quantities which are capable of being extracted from them by friction, as Mr. Mackintosh states to be a part of the Franklinean theory, was proved by the Doctor, as he himself says, to be "contained in glass in great quantity;" and also that it adheres to this substance with so much tenacity that no portion could be conveyed to one side of a piece without expelling an equal quantity from the opposite side. This he explains with his usual perspicuity as follows:-" Suppose the common quantity of electricity

on each side of the Leyden bottle before the operation begins, is equal to 20 ; and at every stroke of the tube, suppose a quantity equal to 1 thrown in; after the first stroke the quantity contained in the inside will be equal to 21; on the outside 19. After the second, the inside will be 22, the outside 18, and so on, till after 20 strokes, the inside will have a quantity of electrical fire equal to 40, the outside none; and then the operation ends; for no more can be thrown into the inside when no more can be driven from the outside. If you attempt to throw more in, it is spewed* back through the wire, or flies out in loud cracks through the sides of the bottle." The correctness of this statement is shown by insulating the jar; in which state the charge proceeds only as sparks are drawn from the outside; and when it is charged, by passing the fluid from the inside to the outside, through an insulated discharging-rod, by which means the communication between the sides being made by conductors, the quantity, say 20, which had been accumulated within, and taken from, without being restored to the latter, an equilibrium is effected, and all signs of electricity disappear. Again, the jar can be charged from itself, by insulating the cushion of the machine, and passing a chain from the outside of the jar (also in a state of insulation from the ground, and suspended by its knob, or ring communicating with the inside, from the prime-conductor,) to the cushion. In this state, on turning the machine, the fluid is drawn from the outside by the rubber, and passes through the prime. conductor to the inside, and thus the charge proceeds with peculiar facility. That the fluid when charged is actually in a state of accumulation on one side, and as destitute of its ordinary quantity on the other, is made manifest to the eye, by passing the charge, while the jar re. mains insulated, through an insulated discharging-rod, the ball in connexion with the outside being removed, and the wire held at the distance of about an inch. In these circumstances the fluid will be seen to rush like a stream from a fountain, from the wire to the external coating;

* I have chosen to retain this rather indecorou term, as peculiarly expressive of the manner in which the fluid is seen to rush from an overcharged jar, plainly showing that it is overcharged, and is throwing off its superabundance.