For two years past, much excitement has been produced in England, by a pro-posal to roof plant-houses with a new kind of rough plate glass, for which a patent has been obtained there by Mr. Hartly. This glass is prepared by a rolling process, which destroys transparency but not translucency; and the benefit said to be derived from it, (and which experiments made under the direction of the Horticultural Society Of London, appear to have confirmed,) is the very important one, that without obstructing the light, this becomes dispersed instead of concentrated, in passing through it, and that no shading is required in the hottest sunshine. Altogether, the subject is so well deserving consideration, that we give our readers the results of the experiments alluded to, as detailed in the Gardener's Chronicle.

"The garden committee directed the rough rolled plate glass to be tried in the garden of the Horticultural Society at Chiswick. For this purpose a small pit, unventilated except by sliding the sashes, and heated by hot water pipes, was selected. In the last week of August this pit was filled with soft wooded plants, which can only be kept in health in the presence of a large quantity of light, among which were the follow-ing, viz: The Begoniasodorata, undulata, ar-gyrostigma, and dichotoma; Torrenia asiatica, Pentas carnea, Adamia sylvatica, Calostylis au-rantiaca, and Achimenes picta. The four Begonias, Calostylis, Adamia. and Pentas bad been cut close back, and were leafless; Torrenia was a cutting just struck, and of Achimenes, the dry tubers were employed. The experiment was thus set in action, without any special care having been taken to make it succeed; on the contrary, everything was against success. It is needless to say, that the months of October, November and December, 1848. were more than usually gloomy, and that neither January or February offered any advantage over those months in ordinary years. In addition to this, it was often necessary to leave the plants in the dark all day long, in consequence of the sashes being covered with frozen mats, which could not be removed.

Nevertheless, and notwithstanding these impediments, the experiment was perfectly successful. On the plants being produced, at a subsequent meeting of the Horti-cultural Society, by Mr. Gordon, to whom the experiment was confided, they appeared in the most beautiful health, with firm, short wood, broad, thick, clean, bright-green leaves, and in the case of the Gesnera and Pentas, flowers per-feet in color, size, and form. In short, it may be said without the least exaggeration, that more perfect examples of high cultivation were never seen, and few so perfect. It was clear that there had been no deficiency of any ele-ment or condition which is required for the most perfect health. This conclusive proof of the excellence of rough plate glass, possesses the highest agricultural interest. It shows that gardeners are now secured effectually from the scorching effects of the sun during summer; and that all the costly, as well as inconvenient contrivances for shading, may be, in future, dispensed with".

So much for the London Horticultural Society. Mr. James Roberts, one of the most successful cultivators in England, who has the care of the grounds of the Duke of Cleveland, at Raby Castle, speaks of this glass as follows:

"At the present time I have nearly 3000 feet of it in use, and I am so far satisfied of its superiority, not only over sheet glass, but also over all other kinds of glass, for horticultural purposes, that for whatever is to re-glaze or erect new here, I will adopt it without hesitation. I use it for plant culture, melons, cucumbers, propagating, etc.; and perhaps no one regrets more than I do, that I cannot replace the sheet in my vineries with it. It is a mistake to suppose that it obstructs light; on the contrary, it collects and diffuses it better than the clearest sheet or crown glass. Another advantage which it possesses, is that there is no scorching and no shading. As to this kind of glass becoming dirty, that has not happened here. It effects a saving of fuel, and is proof against the severest storms".