of Clock JBendulums. 81 



I next made a series of experiments, all of whioh tended to 

 snow that the effects were greatly increased by the removal of 

 the weight belonging to clock 2, I presume from the diminished 

 resistance to so delicate a motive power as that under investiga- 

 tion. I think, therefore, I may fairly confine myself to those 

 experiments in which the weight of clock 2 was removed. 



Exp. 5. — In experiment 5 three slabs of solid cedar, whose 

 entire weight amounted to 13 lbs., were firmly nailed together, and 

 placed on the tops of the clocks, whose feet were placed at about f 

 inch apart. The pendulum of clock 1 was set vibrating through 

 an arc of 6 degrees, and after an interval of about 16m., the 

 hands of clock 2 were set in motion, the pendulum attaining a 

 maximum arc of vibration of 3 degrees nearly. The pendulum 

 of clock 1, whose oscillations had been rapidly diminishing, came 

 to rest 14m. afterwards. 



Exp. 6. — Experiment 6 was made under the same circumstances 

 only that the three pieces of cedar board were placed loosely 

 one upon the other, the nails being removed. In this case the 

 maximum arc of vibration of clock 2 was only 1 3-10 degrees — 

 thus showing plainly that the medium should be a rigid body. 



In the subsequent experiments my time would not permit me 

 to wait for the maximum arc of vibration of clock 2 — though 

 most of them had been previously made with the weight of clock 

 2, on, and with similar results. 



I therefore contented myself with recording the arc of vibration 

 of pendulum 2 at the expiration of 5m. after that of 1 was set in 

 motion. 



This arrangement is quite sufficient for our present inquiry. 

 Exp. 7. — The upper medium employed was a bar of light 

 well-seasoned pine, 4 feet in length, and weighing 3 lb. 6 oz. 



After an interval of 5 m. the arc of vibration of pendulum 2 

 was 30' nearly. 



Exp. 8. — In experiment 8, a bar of the same material, 2 feet 

 long, weighing 1 lb. 12 oz. was employed. After 5 m. the arc of 

 vibration of pendulum 2 was about 27'. 



Exp. 9. — In experiment 9 there was a similar bar 1 foot long, 

 weighing 12 oz. nearly. The arc of vibration was 26' nearly. 



In each of these three experiments, which are very important, 

 the arc of vibration of pendulum 1 had been reduced from 6° to 

 5° 56' nearly. 



Exp. 10. — In experiment 10, a brass tube 3 feet 10| inches 

 long, weighing 13 ounces, was employed as the upper medium, 

 under the same circumstances as before. Here the arc of vibra- 

 tion of No. 2, after 5 minutes, was 32' 2"— that of No. 1, 5° 35' 



Exp. 11. —In experiment 11, a very light rod of wood, 2 feet 



