of cutting. The colours for casing should not remain above two weeks in the pot without being ladled out, and mixed with fresh batch, oxide, &c., as the specific gravity becomes altered by too long exposure to heat, and the Glass injured by evaporation of some of the materials. The severe friction of stoppering is very apt to break cased Glass, unless stopped after cutting; by this means, much of the danger is avoided, especially in single casing. The greater part of the coating being removed by cutting through the exterior, in forming the ornamental pattern, the unequal tension of the two glasses is almost wholly prevented.

It is said that the French first used violet Glass for ripening grapes, and for other horticultural purposes. The rationale adduced was, the partial exclusion of the calorific solar rays, and the greater encouragement of the chemical rays. The experiment has been tried upon a large scale, near London; but whether owing to the glass being too dark a colour, or to unskilful horticultural management, it did not answer. French beans and strawberry-plants under this glass grew rapidly, but were long, spindly, and tremulous; and not appearing likely to come to perfection, the coloured Glass was removed from the greenhouse.

The author tried some of the same Glass in a frame, upon a very fine cucumber-plant, with two branches shooting out in opposite directions, each having blossomed and being about to fruit; when the branch placed under this coloured Glass, became feeble and diminished,—both leaves and fruit being very diminutive, in comparison with the other half of the plant, under the usual , greenish Crown Glass, which perfected its fruit to a large size, and of excellent quality.