DYNAMOMETER. 



over a clock face marked into pounds 

 and hundreds. Leroy's implement 

 is a stronjr spring enclosed in a 

 box of cast iron, and in every re- 

 spect similar to Salter's spring bal- 

 ance. 



The objection urged against these 

 dynamometers is, that the inequali- 

 ties of the soil produces so much vi- 

 bration in the index that no satisfac- 

 tory measures can be made. The 

 following contrivance to obviate this 

 is the best proposed : 



" The improvement consists in the 

 attachment of a small brass pump 

 tilled with oil, the piston of which 

 has one or two small apertures. 



There being no outlet from the pump, 

 it is evident that when any shock oc- 

 curs, caused by a stone, rout, &c., 

 the oil having to pass from one side 

 of the piston to the other, the sud- 

 denness is greatly diminished by the 

 resistance, producing a correspond- 

 ing efTect upon the pointer, which, as 

 these shocks are rapid, vibrates near- 

 er the actual draught of the machine, 

 which is the object in view, and not 

 the measurement of any impediment, 

 but a mean result of the whole." 



Fiff. 1 represents an extemporane- 

 ous dynamometer reconamended by 

 Mr. Cone, in the American Agricul- 

 turist. 



b is the beam of the plough ; c, 

 common swinging trees ; a is an 

 ordinary steelyard hitched on to the 

 clevis and trees : the end of the yard 

 is fastened to a line which passes 

 from the hook of a common spring 

 balance, d, the other end of which is 

 also attached to another line tied to the 

 left handle of the plough. When the 

 horses pull, the steelyard lies in the 

 line of draught, and therefore draws 

 upon the balance, the sliding rod of 

 which is pulled out to an extent pro- 

 portionate to the draught. 



For the purpose of making uniform 

 implements, Mr. Cone proposes that 

 the steelyard be constructed so that 

 1 lb. shall equipoise 32 lbs. near the 

 point of suspension, as in Fig. 2. 

 Adopting this, the measure of draught 

 is readily made ; for if the spring is 

 drawn out to 10 lbs., wc multiply by 



32, and add 10 lbs., so as to make 

 the draught 330 lbs. ; the number of 

 lbs. indicated by the spring is always 

 added to the sum, for that weight 

 would be necessary at the beam end 

 to balance it, and must not be omit- 

 ted. Any steelyard answers ; and we 

 may fasten the line at any convenient 

 mark, taking care afterward to mul- 

 tiply the weight on the yard by that 

 1 on the spring, and adding as many 



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