On the Duration of Muscular Action, 441 



fore might be considered as octaves in music to each other, 

 I sometimes employed notches at greater and sometimes at 

 less distances from each other, bui the result was noverth<j' 

 less ihe.same; and in order lo avoid any error that miglit 

 be caused l)y sonic accidental quality of the souiid ari^:mJT 

 from the length of the muscle employed, or length of 

 the hones concerned in conveying the imitative sound 

 to my ear, I m.idi.* the followmg variation of the experi- 

 j\ient. My ear was stopped by a cushion pres-sed upon by 

 the end of a notched stick that resttd on my foot, aiid thus 

 conveyed the vibraiion from ihe njuscles of my leg to the 

 ear, along wiih tlic tremor produced by fiiction upon tbe 

 noiches ; and still the results were nearly the same; vary- 

 ing in frequency between 20 and HO in ascccnd, according 

 to the degree of force exerted in the experiment *=. 



As a turlher proof that 1 was not much deceived in my 

 judgement of the frequency of ih.ese vibrations, I requested 

 two or three of my friends to repeat the same experiment 

 for me, and our agreement was such as to conlirm me in 

 opinion, that there could be no very ctmsiderable error in 

 the estimate. 



The greatest frequency that I t]|ink I have observed, was 

 about 35 or 3G in a second, and the least was 4s low as 14 

 or 15; but in attempting to lessen the nuniber of vibra- 

 tions, there appears to be a degree of unstiad.ness which 

 prevents any accurate measurement of the real number. 



It is very probable, that in cases of great debility the 

 number may be even considerably less, and n^ay be the 

 reason of that visible unsteadiness, which is known to oc-v 

 cur in persons enfeebled by age, or nmeh reduced by dis- 

 ease. 



Possibly the foregoing observation may not be altogether 

 new to some mcDhcrs of this society, as it is now about 17 

 or 18 years since it first occurred to me, and 1 was then 

 accustomed occasionally to mention it in conversation with 

 my friends ; but I am not aware that atiy other person has 

 made the &ame remark respecting the vibratory nature of 

 muscular action, although 1 find that Grimaldi had ob» 



•The reseir.bUnce of the muscular vibrasions to the sound of camage3 at 

 a disiar.ce, I r^pprelJenc' to arise not so much in.m the ijuality of the sound, 

 as from an agreement in ff-e-iueiicy willi an average of the tremois usually 

 produced by' the run-.bcr of stones in the tegular pavt'ineut of Loudon, 

 passed over by carria|rf6 moving quicklv- 



If the number of vibrations l)e supposed 24 in a second, and t!»e breadth 

 of esch sU-ne be about six inches, the rate of a carriage thus estimated 

 jvould be about eighr milesan hour; which ajjrees with the truth as nearly 

 "as the assuinp:ioii;i u^. which the csu::iaie U founded. 



served 



