We have already alluded to this beautiful, tropical glass house, in which the palms and other trees of the equatorial regions, growing in the ground and in huge tubs, reach the altitude and wear the same aspect as in their native clime. The engraving which forms our frontispiece of this month, will enable our readers to form a more definite idea of its external appearance.

There is no doubt that this is the most beautiful plant house in the world. Though not so large as the great conservatory at Chatsworth, and but small compared with that miracle of size, the Crystal Palace, it has an airyness and elegance that neither of these latter buildings can boast. This is owing to the exterior of the Kew Palm House, or at least the roof, appearing an unbroken sheet of curved glass - while the others, being constructed on what is called the "ridge and furrow" system, presents a series of ploughed or angular roof lines.

The Kew Palm House is one of the largest glass houses in the world - being 362 feet long by 100 feet wide, (in the center,) and 66 feet high. The main ribs of the roof are wrought iron, as well as all the ties. The columns are cast iron, and being hollow, conduct the rainwater from the gutters on the roof to rain-water tanks formed underneath and around the whole interior of the building. A light gallery runs round the whole, from which, not only the best view of the trees and plants is obtained, but the tops of the trees are watered, the supply being obtained from a reservoir in an ornamental tower at some distance.

"The roof is wholly glazed with sheet glass, slightly tinged with green, the tint being given in making the glass, by oxide of copper. This has been done to counteract the injurious effects on the vegetation, arising from the use of white sheet glass, an arrangement proposed by Mr. Hunt, of the Museum of Economic Geology, and practically carried out in this building for the first tune." - (London Builder.

To heat the house, there are 28,000 superficial feet of hot water pipes, connected with several boilers, laid under the perforated iron flooring, which forms the paths, Sec.

No chimneys being visible, the visitor who examines the building is at a loss to know what becomes of the smoke. He is, in answer, shown in the distance, (560 feet off,) a high Italian tower, to which the flues lead under ground. There is a subterranean passage the whole way from the tower to the heating apparatus, and through this passagec runs a small railway with iron wagons to convey the coal and take away the ashes. In ventilation and other details the building is equally perfect.

The entire cost of this conservatory was about $160,000. The rich collection of plants which it contains, and the admirable way in which they grow, are worthy of the great national garden in which it stands, and which the British nation keeps up at a large annual cost, for the instruction and delight of any and every person, without any fee whatever, who wishes to enter.

A pretty picture, and a great work of art. But I cannot help thinking how many comfortable cottages for the shivering and destitute poor, of which England is full, the building of this royal toy would hare made, and how mock comfort the same outlay of money would hare bestowed in some such way. The Palm is a great, grand, and rare plant; and so are the pyramids great, grand, and rare structures; yet I don't see why people might not as well go to Africa, or India, to see the one, as to Egypt to see the other. It is a luxury of which I cannot well see the utility in so much expense.