MECHANICS AXD USEFUL ARTS. 23 



tighter than that on the other, the intermediate gear on the driv- 

 ing coupling will turn slightly, and relieve somewhat the tension 

 on the one wheel, while the other will be revolved in the opposite 

 direction until it comes under the same tension as the first. The 

 ropes that run on these pulleys are a little over an inch in diame- 

 ter. At the speed above mentioned for the pulleys, it will be 

 seen that the speed of the ropes will be about 4,400 feet per 

 minute, or say 50 miles per hour. The difficulty of providing 

 practically for such a speed will be apparent to every one who 

 has had any experience in similar undertakings ; and, as a matter 

 of fact, this has been the great difficulty to be met in carrying 

 out this plan of distribution, and it is only after a long series of 

 trials that this has been successfully accomplished. 



As already mentioned, the driving and driven pulleys at 

 Schaffhausen are of iron, faced with wood ; in other cases, to be 

 mentioned presently, another combination is used, which has 

 given the most satisfactory results. On the opposite bank of the 

 river, or rather a few feet from it, are built some solid stone piers, 

 on which is placed a second shaft and pair of wheels similarly 

 arranged to those in the wheel-house, and high enough to keep 

 the ropes in their transit clear of the water. The shaft is about 

 12 inches in diameter in the body, and 7 inches at the journals, 

 and is supported in iron housings firmly bolted to the piers. By a 

 pair of bevel gears, the motion of this shaft is transmitted to 

 another at right angles to it, carrying another exactly similar pair 

 of wheels, running in a plane in the direction of the course of the 

 river, instead of across it. Coupled to the end of this shaft is a 

 small one, which takes off a portion of the power to some fac- 

 tories situated just at this point on the bank. From the large 

 pulleys, a second pair of wire ropes carries the power to a third 

 pair of wheels, about 400 feet up the stream ; and from here again 

 it is transmitted a similar distance to another pair, and again to 

 another, the pulleys being made with double grooves in their 

 faces to accommodate the two ropes that pass -around each of the 

 intermediate wheels. At any of these points a portion of the 

 power may be taken off, and this is done in a variety of wa} r s as 

 may be most convenient under the particular circumstances ; some- 

 times by gearing and shafting, or again by small pullej's carrying 

 a smaller size wire rope, say half an inch in diameter. On the last 

 span, but one rope is at present in operation, the coupling be- 

 tween the two wheels being locked to prevent it turning ; but new 

 piers and housings are being erected for the purpose of transmit- 

 ting the power to a still greater distance, and then the second 

 rope will be required. As a rule, the speed of all the successive 

 wheels and branch lines of shafting is kept the same, namely, 

 100 revolutions. 



This system of transmitting power to a distance has been a 

 subject of great study during the past 10 years, and is now being 

 applied to much greater distances than those here mentioned. 

 Where longer intervals than, say, 450 feet between the large pul- 

 leys occur, it becomes necessary to provide pulley supports to 

 sustain the weight of the rope. These are made 6 or 7 feet in 



