556 Report on the Exhibition of Implements 



machines tried is reduced from 16 to 5. This arose from the trial 

 in question being a new suggestion which occurred to the consult- 

 ing engineer at a period of the proceedings which did not admit 

 of its being extended to more than a very limited number, those 

 being selected which had acquitted themselves the best in the 

 previous trials. 



The mode of conducting this trial was as follows : — The 

 machines were driven by steam, and the power registered which 

 was required to drive them empty. This gave the friction* of 

 the barn-works alone, and is recorded in col. 6. The friction 

 of the whole machine (i. e., both horse and barn works) is 

 shown in col. 5, and is in fact identical with col. 9 of Table A, 

 the power being given in stones in one case, but expressed 

 in the equivalent horse-power in the other. The difference 

 between these two (see col. 7) gives the friction of the horse- 

 works. This method does not pretend to absolute accuracy, but 

 it furnishes an approximation which will in the opinion of the 

 reporter do much to improve the construction of these machines. 

 Its importance will be best seen by comparing two machines in 

 which the whole friction was about equal, but where it was due in 

 very different proportions to the barn- works and horse-works re- 

 spectively. The machines of Messrs. Garrett and Woods furnish 

 an excellent illustration of this point, the whole friction being in 

 these cases 2"78 and 2*81 ; the friction of the barn-works being, 

 however, 2 07 and 46 ; whilst that of the horse- works was *71 

 and 2 35. It is not an improbable supposition that both of these 

 makers on their return home might have endeavoured to reduce 

 the draught of their machines, and had the whole friction only 

 been ascertained, they would have had no clue to the particular 

 part which was in fault. If therefore they had both endeavoured 

 to improve their barn-works, the result would probably have been 

 that the former maker would have improved his machine, but the 

 latter made his worse ; and if, on the other hand, they had both 

 altered their horse- works, the case would just have been reversed. 

 From the success which attended this first attempt it is probable 

 that the consulting engineer will be prepared at the next meeting 

 to conduct a trial of this kind in a still more complete and satis- 

 factory way ; and it is worthy of remark that it is only by some such 

 method as that above described, in which the draught is ascertained 

 of both horse and barn works combined, that an opinion can be 

 safely given respecting the efficiency of the whole machine when 

 set to work in the farmer's stack-yard. 



* The term "friction," which is used for the sake of brevity, is here intended to 

 represent the whole resistance offered to the acquirement and maintenance of the stated 

 velocity, whether arising from friction, vis inertia?, or any other retarding cause. 



