204 ANNUAL OF SCIENTIFIC DISCOVERY. 



NEW THERMOSTAT FOR REGULATING TEMPERATURE 

 AND VENTILATION. 



This apparatus, invented by Mr. Ward, of England, consists of a 

 series of flat circular hollow cases, about one foot in diameter and one 

 inch deep, attached together in their centers. Each case contains a 

 small quantity of sulphuric ether, which is readily affected by change 

 of temperature. The cases, comprising about six, are suspended one 

 under the other, and to the lowest one is attached a weight by a cord 

 that passes over an excentric pulley. On an increase of temperature 

 the ether expands, and the weight falls clown, and it is drawn up 

 again by the pressure of the atmosphere on the external discs of the 

 cases when the air is cooled. By connecting the weight with the 

 ventilators of a conservatory, or other building, the temperature can 

 be thus regulated to any required degree by a previous adjustment of 

 the apparatus. 



ON THE DENSITY OF SATURATED VAPORS AND THEIR LIQUIDS AT 



THE POINT OF TRANSITION. 



The following is an abstract of a paper read before the British As- 

 sociation on the above subject, by J. J. Waterston. The chief object 

 of the author in these experimental researches was, to ascertain if the 

 low density in saturated vapors holds good up to that point when, ac- 

 cording to M. Cagniard de la Tour's interesting researches, the liquid 

 condition seems to terminate suddenly. The observations were made 

 on the same principle as those which were the means of detecting the 

 general law of density, and the details of which have been commun- 

 icated to the Royal Society. The tubes used by the author were 

 from two to three inches in length, filled with the same liquid in differ- 

 ent proportions, and sealed at the blow pipe. The author then de- 

 scribed the method used in graduating them, and the simple graphic 

 principle employed in calculating the density of the vapor and of the 

 liquid ; the same strictness not being required in these researches as in 

 those detailed in the paper above referred to, in which the strict meth- 

 od of computation is given. The author then described his mode of 

 heating the tubes, which is by suspending them by a brass wire frame 

 in a glass funnel about three feet long, one inch diameter, and one- 

 twelfth of an inch thick, fixed vertically over an argand cocoa-nut oil 

 lamp. The brass wire frame being slipped with the tube into the top 

 of the funnel, kept it in the middle of the current of heated air about 

 four or five inches below the top of the funnel. The liquid volume in 

 Nc. 1 tube being noted, the tube was taken out, and a thermometer 

 put exactly into its place. The mercury quickly rising, the temper- 

 ature is noted after it had become steady. The thermometer being 

 then removed, a second tube, No. 2, was slipped into the same place, 

 and its transition volume noted, then removed, and the thermome- 

 ter substituted, and noted as before. This was the general course of 



