Mr. Editor: - It i» said necessity is the mother of invention. The truth of this is made manifest daily. Necessity and repeated failures are oftentimes the means by which the observing mind traces the cause, and ultimates wonderful scientific practical results, and makes the man of experience.

Such we presume to be the cause that brought out the " Rivers' Orchard House," which is now giving so much pleasure and delight in England, and which is destined to become in this country, and very shortly, too, one of the noblest features in horticulture.

The public have greatly to thank you for the republication of Mr. Rivers' valuable manual. We know that the orchard house can be so designed, arranged, and adapted to fruit and plants, as to comprehend the whole in one magnificent structure; and be assured, Mr. Editor, that if your humble servant only held the influence or power, he would place just such a noble orchard house in a noble position in our New York to be noble park. Why should such a park be without its Sydenham? Surely this would be as appropriate to the grounds as a tower, from whence to gaze at the stars.

With what joy would the citizens of New York and its suburbs, pay their twenty-five cents for admission to feast their eyes and charm their hearts by viewing the beautiful designs of man and the wonderful productions of God. The London trains carry out daily many hundreds to view the great Paxtonian Palace, where man's ingenuity has combined living colors to represent vivid fire, - here, so bright, the glare dazzles the eye, - there, the soft combinations of the rainbow; and yonder in the distance, the lurid fire of one of nature's outlaws bounding through eternal space; - and we stand in awe, wonder, and amazement. The man that has been tippling at the rum-bowl all his life, stands fixed to the spot. He is thinking - absorbed; you see him again entering the interior of the palace; he pauses. The glittering festoons suspended from crystal domes, never before touched his sight, and he seems to be recalling his senses; "is this a reality, or am I in a fairy land!" At length he concludes he will try and grow some of those beauties in his own neglected garden, and he does so.

The money he found for rum, goes now to buy flowers and fruit trees; a higher taste has grown up; the purity of the one has banished the other; horticulture makes good men and intelligent fathers.

The orchard house is the house for the million; - the house for him who possesses a princely income, and him who toils for his daily bread. From a magnificent building capable of growing all fruits, flowers and vegetables, down to the small pit for salads, strawberries, etc. The old notion of requiring large tracts of land for roots to ramble about in, will soon fall to the shades, and the only thing that horticulture requires at the present day is, to have amongst us good practical gardeners, who are good practical chemists. There are plenty of good chemists in the country, and if they had two heads on their shoulders, (gardener and chemist,) gardeners would be much benefited by their experience. It appears to me that when men really know something they think it worth nothing to the public unless it is wrapped up in a lot of mysticism, to let others see they know something that no one else can comprehend; and they use large words where simple, easy terms would express things much better, and be understood by everybody.

But of orchard houses, Mr. Editor. First, the materials of which they should be built; secondly, their construction; thirdly, of the fruit trees and how to grow them, with the kinds adapted for the purpose; and lastly, on the bountiful crops plants are capable of producing in the orchard house properly constructed and managed; - and as these few observations are not needed by gardeners, but are intended for amateurs, I shall call things by their simple terms, so as to be generally understood.

First, the kind of material of which the house should be built. In England, the Rivers house is simple, light and cheap, and well adapted to the mild winters of that country, but here there are contingencies that England little dreams of. In the first place, one of our heavy winter's snows on Mr. Rivers' rafters of fir poles, would make an end of the house and all inside of it. We say, therefore, use strong, substantial rafters; pine, two by seven inches, and placed six feet apart, with three cross bars one and a half by three inches, placed over, or let into the rafter for supporting the glass bars. Make a good strong roof. The bars for receiving the glass can be cut out of one-inch pine boards, which makes them strong enough, one by one inch and a half, and grooved half an inch deep and a quarter of an inch on. These bars are easily got out by the circular saw, and are very moderately cheap.

Mr. Rivers, if I understand him correctly, is of opinion that all fruit trees in the orchard house would be benefited if the temperature of the house did not drop below 26° - so are we. The less freezing that goes on in the roots and branches of fruit trees, the better. The less sun they get on them .when frozen, the better. Let us here suggest that the house be built tight as well as strong. We know what March winds are in England, and bitter experience has taught us what they are in America. It is the gen* eral slaughter month of the whole year.

Build your orchard houses tight, and at the same time put in all the ventilation that you possibly can, and use no hemlock boards.

One summer's sun, and they are all in ribbon strips; - use pine; it can be bought nearly as cheap as hemlock; and also take care to well batten all the ventilators, or they will soon warp and split; my experience is, no wooden ventilator can be made tight unless it is panelled; then they will stand.

Now, in reference to the glazing, the putty should have half white lead worked through it; bed the bars with the putty, and press the glass down tight to the wood; take the putty-knife and smooth off the putty that stands on the upper surface of the glass, and that is all that is required on the outside; there is no necessity of puttying on the upper surface of the glass, as it only cracks and breaks away, and no painting outside will prevent it. After finishing the outside as directed above, paint down each bar with good thick white lead, and you will find the roof to last longer than by any of the present modes of work. You also will be required to take off the extra putty on the inside, and paint as before. Houses built by placing the rafters six feet apart, resting on locust or cedar posts, should have three cross bars between the rafters, one and a half by three inches, to support the glass bars, and placed distant from each other to suit the size of the glass. Houses built in this manner are strong and substantial, have a very nice appearance, and can be built for from two and a half to three dollars per lineal foot, complete.