Further to the discussion on horse whims, I have looked again at "Practical Tunnelling" by  Frederick Walter 
Simms, published in 1844, and quote some of the data he presents.

He quotes the breaking strain of hemp ropes as determined in tests carried out during the construction of 
the bridge built by Thomas Telford across the Menai Straits. These tests gave results showing that 
"Good rope will break with a strain of 2.55 tons per square inch of section". Simms then comments 
"But it ought not to be strained permanently with more then one-third of that, say ¾ of a ton".

He then goes on to quote "the late Dr Gregory" who gave the following rule:

[ (Girth in inches) squared] divided by 5 = load in tons that will break the rope.

The experiments at Menai Bridge were on rope of 5¾ inch circumference, so Simms works out
5¾ x 5¾  = 33.06      33.06 divided by 5 = 6.61 tons breaking strain.
This compares with the experimental result of 6¾ tons.

Simms notes that "for the greater preservation of the ropes, they might be tarred, and payed over with coarse
canvass tarred. Some such covering is requisite for economy's sake, as the wear upon the rope is considerable.
It may be worth remarking that the recently invented wire ropes would in all probability be applicable to the purposes
now under consideration, not only on account of their apparent greater durability, but to prevent the possibility
of wicked persons cutting or otherwise injuring the ropes to cause accidents by their breaking when loaded. Such
a circumstance occurred at Balcombe Tunnel, upon the Brighton Railway, where a rope having been wilfully cut, 
broke at a time when several men in a skip were suspended by it, whereupon they fell to the bottom of ths shaft 
and one of them was killed. This, unhappily, is not a solitary instance."

In the section of his book dealing with the hoisting of water (in the course of driving one of the tunnels they hoisted 
more water than rock), he gives details of the method involved, complete with a drawing of the water barrel (kibble) 
used. The cast iron barrel weighed 174 pounds; the "ironwork" of the bale 104 pounds; and the barrel held 100 gallons, 
which he quotes at 1,032 pounds. The total load to be hoisted was thus 1,310 pounds.

There were nine shafts using horse whims along the line of the tunnel, with depths ranging from 95 feet to 108 feet.
He quotes in detail the register for the whims for 17th September 1842, and some of the results given in his
summary are:
The average of 112 results shows that a horse working 3 hours per day can average 32,943 ft-lb per minute
The average of 212 results shows that a horse working 6 hours per day can average 24,360 ft-lb per minute

Each whim was worked by two horses. The horses were hired at the rate of 7 shillings per day. They were supplied 
by Mr Richard Lewis of Folkestone and were, Simms says, of good quality. Their average height was 15 hands,
and their weight about 10½ hundredweight. They "had as much corn as they could eat, and were well attended to".

His paper on the subject of horsepower delivered to the Institution of Civil Engineers, which I mentioned in my
previous note on this subject, was deliverd "on the evening of March the 14th, 1843".

Tony Brewis