For the following communication we are indebted to Mr. Cranch, Corresponding Secretary of the Cincinnati Horticultural Society, before which it was read. The paper is very interesting, and contains valuable thoughts, but we regret that they are so ill-digested. The length of the letter prevents us from adding any notes of our own at present, interesting as the subject is.

"Cincinnati, O., March 7, 1861.

"D. B. Pierson, Esq.- - Dear Sir: Agreeably to your request for a subject for the consideration of yourself and your horticultural friends, I will suggest that of Motion, or the Vital Force in Vegetation. Much is said by our writers about proper nutrition for plants, while, that which is equally as important is barely hinted at, as though to teach it would produce ridicule from those professing to comprehend all that may ever be known on the subject Vital force, or motive power, is one thing, and food made nutritious for plants by chemical action, is another thing. However nutritious the food may be of itself, it is in a static condition, and can not be transferred to the plant, or tree, against gravity, unless by some adequate force; mere heat can't move it, while heat may cause fluidity and elasticity. Electricity is used to transfer metals, in galvanizing, and as a motive power to machinery, and is doubtless our nerve power, or vital physical principle, derived by combustion of our food and air in our lungs, instead of oxygen, as we are taught, which is merely the heating principle of our natures, instead of vital principle. .

"I will refer you to Patent Office Reports for 1844, pages 368-371, for inter-esting experiments in electricity, quickening the growth of different vegetables. Brown's American Muck Book, page 13, briefly refers to them. We know that the electrical condition of any matter is affected by any change of its density or composition. That chemical action or decomposition sets free latent electricity; that the stirring of the earth by plowing, giving the air and sun access to the decomposable matter of the soil, produces some change, and promotes electric currents; the earth and atmosphere being in different electric conditions, and the • sap being a good conductor, electricity flows and conveys the food, prepared by chemical action, to where it is needed. Unless this is so, why, in said experiments, did the vegetable grow so much faster? The ground was not made the richer by the electrical arrangement. Was it not because there was additional labor performed in supplying the increased nutriment, as in increasing the labor of carrying the bricks for expediting the completion of a building?

"May not Liebig unconsciously derive this motive power by the use of his mineral manures? May not there be greater chemical action, thence greater release of electricity in the ground, when mineral manures are used, .especially if composted with animal and vegetable manures 1 Will not the variety of composition of such a compost intensify chemical action, promoted by the rains, soil, sun and air, and thus furnish to vegetation an increased motive power, to convey the increased nutrition to plants % If so, then it is a question to consider in connection with greater production and vitality of trees to resist disease.

"It is a common thing to hear of peach trees living and bearing forty or sixty years on the high iron lands of Ohio and Indiana. Doubtless, elevation of position has something to do with bearing, while the iron has much to do with the health of the tree and their age. Many will say that new ground is the best, because of its greater supply of nutriment. I will say, because of the decay of that nutriment, creating greater vital activity, without which nutriment would be of no use.

"Field's Pear Culture refers to use of iron for pear trees. Nails and iron have been used to save peach trees. George Graham, Esq., has used iron on pear trees to cure blight. Why? unless because of the electricity generated by the oxidation of the iron, and its being taken up by the sap - as in case of our blood - as a tonic I C. Ferris informs me that he knew of two large pear trees cured of the blight by being struck by lightning.

"Electricity pervades all matter, and that matter can not be changed and retain its latent electricity. Bead Corn Hill Exchange, London, of Robert Clarke, Cincinnati, 1860, p. 167, etc., 'Why we Grow? and you will find life is given out by decaying matter to living matter, loss and gain constantly going on, one equivalent to the other. P. 167 - ' But according to the view which I now propose, decomposition is necessary to develop the force by which organization of food or nutrition is effected, and by which the various purely animal functions are carried on: that decomposition not only creates the necessity, but at the same time furnishes the force of recomposition.' What is this force? is the question. Liebig'8 Complete Works on Chemistry, last chapter, pp. 24-38, on chemical processes and change of place as affected by electricity - see.

"Without being lengthy, many works on electricity may be referred to, showing it to be the silent mechanio at work for us while we are asleep, building up for us our food, etc., its power depending on the intensity of chemical action going on in the soil, arising from diversity of elements of soil, as acids, alkalies, animal, vegetable, mineral manures, nature of the soil, its condition of moisture and porosity, air, sun, heat, and frequency of stirring, and the application of this power to what we wish to cultivate, depending on the ground being free of weeds, etc., which will equally appropriate this mechanical power.

"If in the above experiments referred to, there had been weeds permitted to appropriate a portion of the power developed by the decomposition of the metals used, there would have been less growth of that cultivated. A certain extent of electricity developed naturally or artificially, is essential for a given growth, and if that electricity is partly appropriated to something else, the power being divided, the aggregate growth of the two is but equal to what the one should be; hence the necessity of clean grounds, well stirred, enriched with a variety of manures to favor the greatest chemical action, and development of the greatest amount of mechanical power. If these crude, ill-digested, hasty ideas should prove to be true, on being investigated by competent horticulturists and agriculturists, they should be prepared for the press. Nutriment is one thing, and the motive power to transfer it another. A child might starve if its mother should refuse to carry its food to it. The food would spoil before conveyed, if the child must come to it. The tree must be supplied; neither tree nor food can move of themselves.

Nature has furnished in the food itself during its preparation, its motive power.

"You have scientific associates who would probably be glad to make some experiments showing thus the same soil may be made to produce much more largely by increasing the production of the motive power. It can be done in a hot-house at a small outlay.

"We have valuable manures thrown away in the city, worth more than would support our poor and needy. Ashes, gypsum, blood, and tank refuse, if dried and ground with bones, is as good as guano, hoofs, hair, lime, charcoal, and annual black night soil, etc, dec., and their use effective, if above suggestions are true. Iron pyrites can be had cheap.

" Nature has bountifully supplied us with all sorts of nutriment for vegetation, as well as the working power to combine and rearrange matter. Contact is essential to promote chemical action; hence, necessity of frequent stirring the soil, to allow new air, new sun-heat and light, promotive of chemical action in soil, from which the motive power is derived; while nature furnishes chemical action in the leaves of vegetation, by the action of the sun on the sap in the leaves, and the friction of the winds yielding electricity of the air; the atmosphere, in its electrical condition, differing from that of the earth, begets the negative and positive action sufficient to overcome the gravity, and transfer matter to where needed.

" We see the superior progress and civilization of our day arise from the subjection of physical laws to mental ones, as in the employment of steam power for stationary and movable machinery, chemistry, electricity, etc".

(To be continued).