^g COMPENSATION PENDULUM. 



smaller end was carried through a hole in the top of the 

 case, and projected a few inches above it. In the lower 

 end of the tuhe was inserted the nozzle of a lamp, and im- 

 mediately under it, in the bottom of the case, was a bole of 

 an inch diameter to supply the lamp with air. By this 

 means the tube would communicate as much heat to the 

 internal air, as to raise the thermorneter about tnirty-five 

 degrees. 



Previous to the lamp being put into the case, I made both 

 pendulums vibrate exactly together, and after an interval 

 of twenty-foar hours, the one with the hammered zinc rod 

 had gained, as near as I could judge, one tenth of a second. 

 The mean height of the thermometer was tifty-three 

 degrees. 1 now lighted the lamp, and in about four hours 

 every part appeared to be thoroughly heated, and the ther- 

 mometer arrived at its maximum, which was eighty-eight 

 degrees; at this point it continued with little variation. 

 The motion While the heat was increasing I found the motion of the 

 acceleraiea. pendulum was accelerated. 1 again made them beat ex- 

 actly together, and in about ten hours after, the heated pen- 

 dulum had gained one second; the thermometer in the 

 other case continuing nearly the same. The lamp was then 

 taken out, and as soon as the parts were cooled, and both 

 thermometers showed the same degree, I adjusted the beat 

 of the peiidulums as before, and, nt the end of twetjty-four 

 hours, I found the pendulum that had been heated kept 

 precisely the same rate as it did before the experiment was 

 made. 

 Thependulum ■ By this experiment the zinc rod was evidently too long, 

 adjusted afresh, jj,^ J that by a considerable quantity. The pendulum was 

 then taken down, to have move holes made for the adjusting 

 screw, and after many repeated trials vvith the lamp and 

 tuhe, as before^ 1 found the length of the zinc rod to be 22 

 Ratio of ex- inches, and consequently the length of the iron ones toge- 



p^nsion be ^her ^Q'^Z + 24 :=:■ tl 'i inches, or, the expansion and con- 

 twertii iron and . • ^ , ^ ^ • i i i i <• • i 



hammered traction ot non to ti:at or zinc nammered halt an inch 



2inc. pel- foot, as J5l to 420. " 



When the air Having thm> far satisfied myself with the hammered zinc 



wasrarified tlie rod, 1 |.r()ceede(.»l to make similar trials with the one that 



»-^co{vibrmon ^^^ unhammered; in doing which, a circupsi^ce gccorred,, 



"• ' ^' " that 



