On we go to the upper gallery, and find the gigantic reflectors for illustrating the laws of reflection of heat, light, &c., which, singularly enough, are governed by the same law; sometimes by these instruments a mutton-chop is placed in the focus of one of them, and at one hundred feet distant a fire is placed in the other; the result is, that the chop is cooked, or a candle may be lighted by the same means at the same distance: this is by reflection. Well, another bang of the gong, and away we go to hear a Lecture on “the Process of Marbling and Decorating Paper.” By-the-bye, that gong is a curious instrument, being composed of a large steel spring, coiled round in an open coil, and terminating in a standard. On being struck with a hammer it emits a melodious sound, like the tone of a church bell, for which it has been proposed to be used, and is patented for this purpose; and no doubt, in a short time, these instruments will be so improved and tuned, so as to do duty for a whole peal of bells. The Marbling of Paper has never yet been made public, the trade having carried the process on in perfect secrecy, so as to retain a monopoly—which is a very bad thing, as it prevents many improvements being made, which would much increase its sphere of utility; the simplicity of the process, however, has been now brought forward by the public spirit of a gentleman named Woolnoth, to whom the world should be much obliged for upsetting monopoly, and breaking down principles which tend to frustrate rather than accelerate improvements in science. The process commences by making a solution of the “gum tragacanth,” and which is called in the shops, “gum dragon;” this solution being brought to a proper consistency, is placed in a long flat vessel, sufficiently superficial to allow a large sheet of paper to be placed on its surface. Well, having prepared this apparatus, which requires great nicety, the workman, having his colours already mixed, sprinkles on the surface of the gum solution a sufficient quantity, first of one colour and then another, until he obtains the required pattern. But the philosophy of obtaining this pattern remains to be told. The colours are mixed with such materials as cause them to repel when they come in contact with each other, in the same manner as oil does when dropped on water. The material thus made use of is gall taken from the bladder of an ox. This substance has the curious property of preventing the colours from mixing with each other; for instance, if a sprinkle of lake be first put on the surface of the gum (there being no absorption of colour as there would be on paper,) and another colour having gall ground with it be sprinkled over this, the two colours, instead of mixing, would immediately repel each other, and form a curious pattern, each colour forming its own particular shape, and this may be carried on to any number of colours; it is applied to various purposes, such as covering copy-books, and