pronounced unsafe, then if greater shielding is recommended the question is, what means have we for detecting small quantities of fire-damp? It would seem from the foregoing remarks that in any existing safety-lamp, where one qualification is increased another is proportionately reduced; so it is doubtful whether all the necessary requirements of sensitiveness, resistance to strong currents, satisfactory light, self-extinction, perfect combustion, etc., can ever be combined in one lamp. The object of the present paper is to show that with the assistance of the fire-damp detecter, the tin shield, or any other description of lamp, is made as sensitive as the Davy, while its other advantages of resisting velocity, etc., are not in any way interfered with. As a proof of this I may mention that a deputy of experience recently visited a working place to make his inspection. He reported the stall to be free from gas, but when the manager and steward visited it with the detecter, which they applied to the roof (where it would have been difficult to put even a small Davy), it drew a sample of the atmosphere which, on being put to the test tube in the tin-shield lamp, at once showed the presence of fire-damp. Out of twenty-eight tests in a mine working a long-wall face the Davy showed gas only eleven times, while the detecter showed it in every case. The detecter, as will be perceived from the one exhibited, and the accompanying sectional drawing, consists simply of an oval-shaped India rubber ball, fitted with a mouthpiece. The diameter is about 2¼ inches by 3 inches, its weight is two ounces, and it is so small that it can be carried without any inconvenience in the coat or even in the waistcoat pocket. Its capacity is such that all the air within it may be expelled by the compression of one hand.