TRANSACTIONS OF THE SECTIONS. H 



give images of every size useful to an artist, up to the largest panoroma ; by this Mr. 

 Horner traced the great panorama of London from the top of St. Paul's. The exist- 

 ence of this instrument caused the Colosseum to be built. Through this instrument 

 original sketches may be printed from. By taking the flat speculum from the ob- 

 ject-end the images will be given the reverse way, and thus suited to trace direct on 

 stone. 



Observations on the Deiisity of Saturated Vapours and their Liquids at the 

 Point of Transition. By J. J. Waterston. 



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

 the low density in saturated vapours holds good up to that point when, according 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, the details of 

 which have been communicated to the Royal Society. The tubes used by the 

 author were from 2 to 3 inches in length, filled with the same liquid in different pro- 

 portions and sealed at the blowpipe. The author then described the method used 

 in graduating them, and the simple graphic principle employed in calculating the 

 density of the vapour 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 method 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 3 feet long, 1 inch diameter, and y\th of an inch thick, fixed vertically 

 over anArgand 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 4 or 5 inches below the top of the funnel. The liquid volume in No. 1 tube 

 being noted, the tube was taken out and the thermometer put exactly into its place. 

 The mercury quickly rising, the temperature 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 thermometer 

 substituted and noted as before. This was the general course of observations ; 

 when the temperature had to be carried above 600°, a funnel only 18 inches long was 

 used. The state of the liquid in the tube was closely examined by means of a 

 watchmaker's lens, and could at all times be seen distinctly by transmitted light. 

 One set of tubes were of hard Bohemian glass, one-eighth of an inch bore and one- 

 fiftieth of an inch thick. These sometimes burst when the pressure was calculated 

 to be about 400 atmospheres, if the laws of density and pressure hold good at these 

 extreme points. The force of the explosion was quite what might be anticipated : it 

 was as if the liquid, which never exceeded three grains in weight, had been ful- 

 minating powder. The thick glass funnel was shattered into small fragments 

 immediately opposite the tube. Other sets of tubes were of soft glass, one-twentieth 

 of an inch thick and one-fifth or one-sixth of an inch bore. None of these burst ; at 

 a very high pressure one merely gave way, breaking across into three pieces as if cut 

 by a file. The author then gave the details of his experiments in a tabulated form, 

 each noting the low temperature and volume, the maximum volume and temperature, 

 and the transition volume and temperature, with notes of the successive appearances 

 noted in the liquid at its surface and in the vapour. The surface of the liquid at one 

 stage always assumed a flat form, showing cessation of capillarity ; often assumed 

 a conoidal form, wasting at the apex ; sometimes two surfaces showed themselves ; 

 the conversion currents seen clearly in the early stages often changing into zigzag 

 motions of spherules of vapour at the transition point. In this way the author ex- 

 amined sulphuric sether, alcohol, sulphuret of carbon, distilled water, chloroform, 

 dichloride of sulphur, anhydrous oil of turpentine, acetic acid, and sulphuric acid. 



On a Laio of Mutual Dependence between Temperature and Mechanical 

 Force. By J. J. Waterston. 



The author began by stating that the experiments performed by MM. Gay-Lussac 

 and Wetter, and agairi by MM. Clement and Desormes, to discover the ratio of 



