122 



Mr. J. J. Waterston on the Expansion 



§ 12. Mode of conducting the observations. — The figures 1, 2, 3, 

 and 4 (PL II.) show the arrangements adopted. The heater, C G, 

 is a thin brass tube 2 inches diameter and 27 inches long, held 

 vertical over Bunsen-flames by screws as shown in figs. 1 and 2. 

 To a length of 8J inches down from the top two slits were cut 

 one inch wide and exactly opposite. To these were applied slips 

 of plate glass (G G, fig. 2). One inch lower down a plate of 

 talc was fixed to intercept the upward current of heated air 

 from the lower part and direct it upon the upper end of the tubes. 

 An inspection of figs. 2, 3, and 4 will show the size and position 

 of this plate, without which the observations would have been 

 impracticable. 



The tubes of oil and water 0, W were suspended as shown, 

 having a small cork stuck on at the lower end of the water-tube. 

 The additional glasses on the slit near which the tubes hung were 

 required to prevent loss of heat by radiation. A lens was used in 

 reading the position of the bottom line of the capillary cup of the 

 liquid on the scale. It is a very distinct object by transmitted light. 



The only way to avoid the difficulty caused by corrosion of 

 the glass, is to make the preliminary arrangement so that a single 

 series of observations shall complete the range of temperature in 

 as short a time as possible without expecting a second from the 

 same tube. The temperature must always be kept ascending, 

 and is regulated by the stopcock (s, fig. 1), which ought to be 

 made, if possible, so that the angular motion should increase 

 the flame at a uniform rate. The readings are taken when, 

 although the temperature is still ascending, it is going very slow. 

 The gas-cock is then touched slightly to increase the flame a little, 

 then another observation, and so on. A windy day is to be avoided. 



§ 13. The following series was completed in less than an hour ; 

 the tubes in situ are shown in fig. 3, and the top surface of liquids 

 at the beginning and end are marked at /3 and e. The glass of 

 the water-tube appeared but slightly acted on, and there was no 

 sensible absorption when afterwards examined. No liquid had 

 collected in the top cone, and the highest observation was quite 

 distinct and unexceptionable. 



Oil. 



Water. 



Temperature CM. by 



Oil. 



Water. 



Temperature CM. by 



Inch. 



Half inch. 



Acid- tube. 



Oil-tube. 



Inch. 



Half inch. 



Acid-tube. 



Oil-tube. 



-0 035 



0-89 



o 



10 



o 



10 



+0-960 



3-48 



2977 



303-7 



+0-650 



2-23 



225-3 



224 



0-950 



3-40 



295-3 



301-3 



0750 



2-58 



250 



251 



1-030 



3-90 



3117 



3207 



0-800 



273 



262 



263-5 



1050 



396 



3158 



325-5 



0-840 



2-97 



271 



2738 



1060 



407 



3175 



327-9 



0-850 



300 



273-5 



2763 



1075 



417 



320-5 



331-4 



0-900 



3 15 



284-6 



288-9 



1100 



4-27 



325 5 



337-4 



0925 



330 



290 



295 1 



1115 



4-47 



3283 



3410 



0-950 



3-43 



295-3 



301-3 



1120 



4-48 



329-3 



3420 



