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.
Messrs. Negretti and Zambra have arranged a Wet and Dry Bulb Hygrometer upon the same plan.
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