ensuring that none but the mercury in the tube can be transferred into the indicating column; E is an enlargement made in the bend so as to enable the mercury to pass quickly from one tube to another in revolving; and F is the indicating tube or Thermometer proper. In its action, as soon as the Thermometer is put in motion, and immediately the tube has acquired a slightly oblique position, the mercury breaks off at the point D, runs into the curved and enlarged portion E, and eventually falls into the tube F when this tube resumes its original perpendicular position. The contrivance for turning the Thermometer over may be described as a frame with a vertical propeller; to this frame the instrument is pivoted. On its descent through the water the propeller is lifted out of gear and revolves freely on its axis; but so soon as the instrument is pulled towards the surface the propeller falls into gear and revolves in the contrary direction, turning the Thermometer over once, and then becoming locked and immovable. _Directions for adjusting the Thermometer previous to its being lowered in the Sea._ I. The mercury must all be in the left-hand column. II. The short peg at the back of the thermometer must be in front of the stop plate S +; in order to effect this, pull the knob which stops the Thermometer, and slightly turn the propeller, to make the Thermometer advance sufficiently to escape the stop plate. Negretti & Zambra's Patent Atmospheric Recording Thermometer, Fig. 3, differs from the Deep-sea Thermometer by its not having the double or protected bulb, it not being required for resisting pressures. In this case the instrument is turned over by a simple clock movement, which can be set to any hour it may be desirable; the Thermometer is fixed on the clock, and when the hand arrives at the hour determined upon, and to which the clock is set as in setting an alarum clock, a spring is released and the Thermometer turns over as before described. [Illustration: Fig. 2.] [Illustration: Fig. 3.] Messrs. Negretti and Zambra have arranged a Wet and Dry Bulb Hygrometer upon the same plan. NEGRETTI & ZAMBRA'S PRICE LIST OF STANDARD METEOROLOGICAL AND OTHER PHILOSOPHICAL INSTRUMENTS. _The marginal figures in this List and the numbers of the wood engravings refer to paragraphs in "Negretti & Zambra's Treatise on Meteorological Instruments."_ L s. d. 4 =Standard Barometers=, Fortin's arrangement, as Fig. 3 with mahogany board 8 8 0 Ditto ditto with Millemetre and English scales 9 9 0 Ditto ditto with tube, 0.45 internal diameter and millimetre scale 10 10 0 =Observatory Standard Barometers=, extra large tubes and cisterns L25 0 0 35 0 0