It appears to me that it would be a wise exertion of authority, to insert in every act of Parliament granted for incorporating Gas-light Companies, a clause prohibiting the proprietors from ever conveying the waste material, or any other produce from the manufacture of coal gas, either directly or indirectly into the common sewers, drains or water courses, or into rivers and lakes adjacent. The salubrity of the water we use is of as much consequence to us, as any superior excellence or saving of cost in our light can possibly be, and we ought to take care that in profiting by an improvement which science and art have discovered, we do not unnecessarily depreciate one of those primary blessings we owe to the bounty of nature. _Lime Machine lately adopted._ In the improved purifying apparatus[38] lately brought into use, of which we shall now give an account, a shaft or axis furnished with teeth or claws, is applied within the interior of the vessel, and made to act in such a manner as to scrape out the openings or slits through which the gas has to pass every time the axis is moved round, and by which regular clearance all chance of stoppage is avoided without any augmentation of the purifying mixture. [38] This machine has been adopted at the gas works at Chester, Birmingham, Kidderminster, Bristol, and in many other provincial Gas Establishments. The lime trough is also made moveable on a centre or axis, in such a manner that it may readily be inverted by a lever from the outside, for the purpose of emptying its contents into the bottom of an exterior vessel, from which the waste materials may be discharged at pleasure. With this machine we are farther enabled to employ the purifying mixture in a semi-fluid state, and consequently in a much less bulk; and after having suffered it to remain in the reservoir destined to receive it, the waste substance speedily acquires such a degree of solidity that it may be dug out with a spade and carted away in a small compass. The safety of the apparatus is therefore insured and the construction of expensive drains and sewers is rendered unnecessary. The following description will render the construction of the improved apparatus obvious. A, A, fig. 2, plate II., is a rectangular four-sided prism, made of cast-iron plates, screwed together air-tight with bolts and cement. The base of the prism terminates in a rectangular four-sided pyramid placed with its apex downwards. It is surrounded by an iron stage, supported upon pillars, as shown in the design.