702 
Report on Implements at Preston. 
Mr. Corbett's 3-horse set, No. 2438, illustrated in Fig. 6, was 
accidentally subjected to a trial of great severity. In crossing 
the site of an old ditch that had been filled in, the share of the 
digging plough to which it was attached struck upon the buried 
root of a large tree ; the ploughshare was broken, and the 
whippletree was crippled at the same time. The ash pomel- 
tree that took the draught of all three horses was uninjured, but 
one of the steel whippletrees was so bent and twisted that it could 
not be used again without sending it to the smithy. We could 
wish for no clearer demonstration of the truth that neither steel 
nor iron should be used in a solid form for whippletrees. It 
may be noticed that Mr. Corbett is not altogether singular in his 
preference of wood for the greatest transverse strain. On the 
first stand in the Yard, Messrs. J. L. Larkworthy and Co. ex- 
hibited three sets of whippletrees, but did not enter them for 
competition. Two sets for two horses were each of steel, but in 
the three-horse set the pomel-tree was of wood, and the minor 
trees of iron. Lest any one should attach too much importance 
to this adherence to old custom, forgetting that the old proverb 
experientia docet may sometimes be fairly rendered " experience 
does it," it may be well to mention that, a few stands further on, a 
set of whippletrees was shown with ash-bars of oval section sub- 
jected to a strain of compression only, the oval form being of 
course right when subject to a transverse strain, but as senseless 
for a mere strain of compression as it would be in a walking- 
stick. 
It is much to be regretted that I cannot give the exact 
strength of the well-trussed steel whippletrees, and compare 
them in weight and strength with old-fashioned wooden ones ; 
but there is no doubt whatever that the set that obtained the 
prize in Class VI. is amply strong enough to take a full four- 
horse strain. The question may here be raised, however. Is it 
absolutely necessary to make whippletrees so strong, that when 
an accident occurs in the field they shall be able to suddenly 
pull up the horses without injury to the trees? That is, are we 
to reckon the 4-horse strain as the force exerted in steady work, 
or in the sudden jerk that stops them ? In most engineering 
work it is not left to chance to determine the part that shall give 
way whenever the strain exceeds the power. If every part of 
the harness and of the implement is made of greater strength 
than the horses, we save our tackle at the expense of our live- 
stock. It would be better policy to choose some point or points 
(the hooks or the traces, for instance) that shall break with a 
strain more than a horse should be subject to. A safety-valve 
of this sort would often be of use when valuable animals are 
attached to valuable implements. If no such provision is made, 
