86 A Letter to the Dublin Society 



prevent tiicm from being forced out of their proper direction by 

 the effort of the sprinp;s, or the giving way of any part of the 

 work, which fastens the axletrees to tlie carriage. 



The apraratus u-ith which the foHuv, ir.j^' e :penments were 

 tried, is fully described in the annexed Report. By the Hberal 

 supply of men from the commissariat, I was enabled to carry on 

 the experiments with facility. 



Part of the weig!)t in the following experiments on two- 

 wheeled carriages was sustained by the guide-pole; the quantity 

 of this weight was determined from time to time by a steelyard. 

 It seldom varied ; but to ascertain the ratio of any inaccuracy 

 which might arise from this circumstance, when the carriage 

 was loaJed with nine hundred and three quarters, and when 

 twentij pounds were placed on the guide-pole, it required four- 

 teen pounds to draw it. \\I\\Gn forty pounds were placed upon 

 it, it required fourteen pounds and a half to draw it. 



There could not have been a difference of more than three 

 or four pounds in the weight upon the pole in any of these three 

 experinr.ents, wliich could not affect the draft to "the amount of 

 more than two ounces. 



Of the Effects of Springs on twn-ivheeled Carriages. 

 Two carriages of similar construction, except that one had 

 no springs, and that the other had grasshopper springs, were 

 compared. 



cwt. (jrs. ll's. 

 The carriage without springs weighed . . . . .3 1 



Ditto, with springs 3 27 



To the carriage with springs, was added . . 4 3 21 

 Making in the whole g 2 o" 



The carriage without springs weighed . , . . 3 1 

 And carried a weight of 2 1 7 



Making in the whole 5 2 7 



It appears that the carriage with the springs carried 2cwi;. 

 Sqrs. 2 ! lbs more than the carriage without springs, yet on trial 

 it rather preceded the other. 



The sane carriages were again compared, substituting elliptic 

 for grosshon,jer springs ; 2qrs. 7 lbs. were added to the carriage 

 without sp-ings, to louke up the additional weight of the elliptic 

 springs, and the springs beiug prevented from actitig by blocks, 

 the two carriages kept togc-tlier. 



The springs being permitted to act, there was added to the 

 carriage with springs 2twt. Iqr. They then kept together. 



Then 



