94 



Mr. H. Tomlinson. The Influence of 



quencies than those marked on the forks, rendered it evident that it 

 was possible to determine with great accuracy the vibration. number 

 of a tuning-fork by means of the syren, when the notes of these two 

 instruments are compared directly with one another.* The case, how- 

 ever, was different when a monochord was tuned to the note of a fork, 

 and the former then compared with the syren. Thus the monochord 

 was tuned to unison with a Koenig's fork marked 384, and afterwards 

 the vibration-frequency of the former was determined by the syren. 

 Two trials resulted in giving the number of vibrations per second as 

 387 and 386. In a similar manner, using a fork marked 512, six trials 

 with the syren gave the vibration-frequency as follows : — 515'8, 516"8, 

 5143, 515 - 8, 516*8, 515'4, with a mean value of 515'8. The experi- 

 ments with both forks therefore gave values for the vibration- 

 frequencies which were about f per cent, too high, and yet the mono- 

 chord after these trials was in each case still in perfect unison with 

 the fork with which it had been compared. As the assistant 

 (Mr. Furse) seemed to think that the error arose from drawing the 

 bow too strongly across the wire of the monochord, in the endeavour 

 to make the sound of this instrument of sufficient intensity to be heard 

 at the same time as that of the syren, a screen was placed so as partly 

 to shield the sound of the latter from the manipulator of the mono- 

 chord, and this plan proved to be successful, for now the syren 

 recorded the same vibration-frequency for both monochord and 

 tuning-fork, and several experiments of the same kind with forks of 

 different pitch manifested that with the precaution mentioned above 

 the syren could be made to determine the pitch of the monochord as 

 accurately as the pitch of the tuning-fork. 



Matters having been so far satisfactorily arranged, a considerable 

 number of trials were made, for the purpose of deciding on the best 

 mode of arranging the wire which it was desired to throw into longi- 

 tudinal vibrations. In the first instance the wire to be examined 

 was stretched horizontally, and clamped at one end to a block of iron 

 secured to a window-sill. Towards its other extremity the wire 

 passed over a fixed pulley, so that by placing weights on a scale-pan 

 attached to this extremity any required degree of stress could be put 

 upon the wire. Before going over the pulley the wire passed through 

 the jaws of a strong vice, so that when stretched sufficiently it could 

 be firmly clamped by means of the latter, and was protected from 

 injury by placing pieces of hard wood between it and the jaws of the 

 vice. Both the vice and pulley were firmly clamped to a very stout 

 table. When fixed for examination the wire was thrown into longi- 



* The author has again to thank Mr. Kurse, the curator of the Museum of King 

 G-eorge III, at King's College, for his assistance ; as also Mr. H. A. Beatchlous, one 

 of the students of the Physical Laboratory. Both these assistants are musicians, 

 and the former is especially remarkable for his skill in manipulating the syren. 



