494 



Messrs. Stewart and Loewy on the true 



[June 17, 



should have liked to see their number much increased. To avoid a cor- 

 rection for pressure, we took care to correct at once, before beginning an 

 experiment, the reading of the gauge to 32° of temperature, and to 

 regulate by a few strokes of the pump the pressure, so as to assimilate it 

 to the mean pressure (also reduced to 32°) of the experiments pre- 

 viously made in cold air. All pressures are reduced to 32°, and the 

 small difference of pressure which still resulted, comparing the mean 

 of the hot-air experiments with those in cold air, amounting to about 

 Y^o" °f an inch, has been disregarded in the final reduction. 



An attempt to test the constancy of the temperature-correction in 

 vacuo, with reference to a suggestion made by Colonel Walker, Super- 

 tendent of the Great Indian Survey, who suspects that the coefficient ot 

 expansion of a pendulum in air varies slightly from that in a vacuum, 

 proved a failure. The pomatum which is used for tightening the dif- 

 ferent parts of the receiver melted by the heat of the stove, and rendered 

 it impossible to reduce the pressure in the receiver sufficiently for the 

 purpose of the experiments. 



I. Experiments made in cold air. 





II. Experiments made 



in hot air. 



No. 

 of 

 exp. 



Tempe- 

 rature. 



Pressure. 



No. of 

 vibrations 

 per day. 





No. 

 of 

 exp. 



Tempe- 

 rature. 



Pressure. 



No. of 

 vibrations 

 per day. 



i. 



2. 



3- 

 4- 

 5- 

 6. 



7- 

 8. 



9- 



IO. 



ii. 



47-84 

 4777 

 46-33 



46- 25 



4772 



47- 91 



48- 43 

 47-76 



45- 09 



46- 19 

 47'5° 



inches. 

 30*052 

 30-1 12 

 30-182 



29- 938 



30- 460 

 29-498 

 29-582 



29- 328 



30- 202 

 30-011 

 30*107 



86013-60 

 86013*76 

 86013*82 

 86014*02 

 86013-58 

 86013*64 



86013- 98 



86014- 40 

 86013-90 

 86013*99 

 86013-61 



<c 



■s 



02 

 t3 



8 



xn 



1* 



( 



2. 

 j 3- 

 ^ 4- 



5- 

 [6. 







70*6 



7i*3 

 72*1 

 70-8 

 73-8 

 82*5 

 82*5 

 83*9 

 88*3 

 • 90*8 

 99"9 



inches. 

 29-964 

 29-970 

 29958 

 29-950 

 29-960 

 29-914 

 29-988 

 29-960 

 29-941 

 29-982 

 29-971 



86002-72 

 86002-64 

 86002-50 

 86002*90 

 86002-43 

 85997-84 

 85997-10 



85995-65 

 85992-23 

 85992*73 

 85988*43 



The following are the mean results, with their respective differences : — 



Temp. Pressure. Vibra- 



inches. tions. 



A. Experiments in cold air 47*i6 29*952, 86013*85 



B. Experiments in hot air, first set 7 I- 64 29*960 86002-64 



C. Experiments in hot air, second set .. . 88*oo 2.9-959 85994-00 



Resulting differences of temperature and number of vibrations : — 



Temperature. Vibrations. 



o 



A~B = 2448 1 1 -2i 



A~C = 40*84 19*85 



B~C ~ 16*36 8*64 



