166 ANNUAL OF SCIENTIFIC DISCOVERY. 



grade scale on the dial. These thermometers are correct, portable, easily 

 read, and very quick, since the expanding metal is in direct contact with the 

 air, which enters the cases by holes made for the purpose. Metallic ther- 

 mometers, especially Breguet's, are used in laboratories to measure very 

 minute variations of temperature, but they are very dear. Mr. Beaumont 

 has succeeded, by means of well-adapted tools, in making them cheaper 

 than accurate mercurial thermometers. And he adapts them to several uses, 

 for which they are unrivalled, namely, for vacuum sugar-pans, gas-workers, 

 measuring temperatures below the freezing point of mercury, measuring 

 the temperature of super-heated steam and of hot-air furnaces, up to 

 1.200 Fahrenheit. 



DEEP-SEA THERMOMETER. 



The principle of a new deep-sea thermometer, devised by Mr. Wentworth 

 Scott, of England, is as follows: The upper portion of the thermometer 

 (glass) tube terminates in a capillary orifice, bent at a right angle to it, and 

 enclosed in a vacuum chamber, the lower part of which contains mercury. 

 By inverting the thermometer the mercury runs from the bulb up the stem 

 and through the orifice, until the latter is covered and a vacuum left below. 

 The reservoir bulb is then slightly elevated, and a portion of mercury runs 

 back again, leaving the thermometer tube quite full to the point of the capil- 

 lary orifice. In this condition it is obvious that any additional heat must 

 cause the mercury to flow out of the orifice in small drops, which are, so to 

 speak, helped out by a fine platinum wire, which prevents the formation of 

 large drops. Upon cooling, the mercury sinks, and the vacant space, left by 

 the effusion of a portion of it, is a measure of the heat to which the instrument 

 has been exposed, and it is graduated so as to facilitate the necessary calcu- 

 lations. 



ON THE USE OF STEAM EXPANSIVELY. 



Much interest is now felt among engineers as to* the economy of using 

 steam expansively. Mr. Isherwood, chief engineer of the United States 

 Navy, after a long series of experiments in the Brooklyn Navy -yard, came 

 to the conclusion that there was no appreciable advantage derived from 

 working it expansively. Recent experiments at the Metropolitan Flouring 

 Mills, in New York City, where there are two pairs of very fine engines, 

 indicate, also, that there is no advantage in it, in spite of the very evident 

 theoretical gain. 



CAUSES OF COLD ON HIGH MOUNTAINS. 



A recent number of the Annales de Chimie et de Physique contains an inter- 

 esting paper, by M. Martins, on the above subject. He treats first of the 

 action of solar rays, and the absorption of their heat by the atmosphere in 

 proportions varying with its density. In consequence of the greater rarefac- 

 tion of air on mountains it stops less of the solar heat, and hence, in clear 

 weather, the sun's rays exert a greater heating power upon the earth than 

 they do at a lower level. Repeating, with better instruments, some experi- 

 ments of Saussure, he came to the same conclusion ; and asserts that the solar 

 heating power is greater on a mountain than in the valley, although tne 

 temperature of the air was twenty-two degrees lower. The difference was, 

 however, only slight, amounting only to a fraction of a degree (centigrade). 



