252 



PROFESSOR TAIT ON IMPACT. 



0i, [0 



[SO 



[100 



/8 2 ,[0 



[-80 

 [-100 



yp[0 



[30 

 [60 



y 2 -[o 



[-30 

 [-60 



S t ,[0 



[20 

 [40 



Mo 



[-20 

 [-40 



-118 

 1682 

 3317 



-118 

 150-6 

 300-1 



1315 

 1710 



2890 



1315 

 1710 

 2900 



2326 

 2510 

 3058 



232-6 

 2508 

 3054 



/ = -118 + 146-O9(0) 2 

 )■=- 117-8 + 13O-33(0-O368) 2 -75] 



r=131-5 + 14314(0+-OOl7) 2 

 r = 131 5 + 14445(0 --0007) 2 

 r =232-6 + 149-37(0+ -0019) 2 



r= 232-6 + 14937(0) 2 



[55] 



166 



18 



[70] 



100 



101 



[90] 



242-4 



244 



[-70] 



85-5 



88-6 



[-75] 



116 



118-2 



[-90] 



2175 



2190 



[15] 



1415 



141-5 



[45] 



219-8 



2202 



[-10] 



135-9 



135-9 



[-50] 



241-8 



2413 



[-65] 



3170 



317-2 



[10 ] 



237 



237-2 



[30 ] 



274 



273-8 



[40-5] 



327-6 



327-3 



[-30 ] 



2735 



2735 



[-40-75] 



327-6 



327-8 



DESCRIPTION OF THE PLATE. 



The chief figure is, as above stated, photo-lithographed on the scale of - 3 from the record of a 4-foot 

 fall on Vulcanised India-rubber. Even in this reduced scale it shows fairly enough the relative details of at 

 least eight of the successive rebounds. These are numbered in order. The original showed several more. 

 As its lines were not only very fine, but in blue, they had to be carefully gone over with a photographically 

 inactive colour, so that much of the more delicate detail is unavoidably lost. The tuning-fork was kept in 

 contact with the disc for a little more than a complete revolution. The consequent overlapping of the trace 

 enables us to see that the angular velocity had not sensibly changed during one revolution of the disc. 



The three figures immediately below are (pencil) records of successive impacts on Native India-rubber 

 (9/1/89). Time of rotation of disc s -3. 



Then follow records of impacts on Pine Tree (7/11/88) from heights of 8, 4, and 2 feet. These show the 

 " wriggles " spoken of in the text. Time s- 3. 



The group of five which follows belongs to the experiment III. of 23/7/90 with Plane Tree, whose details 

 are given in the Table. Some of these show traces of wriggles. 



The final group contains details of the first eight successive impacts of IV. of 7/6/90 on Vulcanised 

 India-rubber. To save space, the first and third, as also the second and sixth, which took place at the same 

 portions of the datum circle, have been drawn together. 



In each of the two later groups the time of rotation of the disc was a little more than one second. 



The disc always had positive rotation; so that the older figures (those in pencil) must be read the 

 opposite way to the others, which were reversed in printing from the disc : — i.e., the compression part of the 

 impact is to the left on the pencilled figures, to the right on the others. 



