smoothly. Practical results are what we want, without going into an argument as to the best devices to show in figures what the best humidity may be. We are able, by means of the Aerophor, to provide moisture in the weaving and other rooms where it is advantageous; and we are ready to put up machines in any mill to show whether our statements are well founded, and will take them down again if they are not; without any charge either for putting up or taking down.

Mr. SAUNDERS. In regard to the last inquiry, I will say, any ordinary wet and dry bulb thermometer will give the changes that will occur in a card-room or spinning-room sufficiently to know what to do. I think that is about all we can do. If we have our instrument in proper condition, with clean water, distilled water, and the wick kept perfectly clean, as we see by the reading of that paper, it shows pretty conclusively that a wet and dry bulb thermometer will be sufficient, and that with a little care almost any overseer would be able to control it.

A MEMBER. In our experience the wet and dry bulb thermometer was not taken care of unless we had somebody especially to take care of it. In looking over Mr. Saunders' paper, and comparing the readings we took in our mills on the same day in Connecticut, I find that the Wamsutta Mills compared quite closely with the readings we took with that instrument in our spinning-room. I think it did not vary more than four degrees on the same day and the same time of day.

The PRESIDENT. Has any other gentleman a word upon this subject? If not, we will take up the next subject on the programme. Mr. W. H. DODGE of Indiana will present a paper on ROPE DRIVING.

TRANSMISSION OF POWER BY MANILA

OR COTTON ROPES.

By WALLACE H. DODGE, Mishawaka, Ind.

For the transmission of power we have had, for ages, two main methods employed, viz., toothed gearing and the horizontal revolving shaft with the pulley and belt. These are only capable of transmitting power very short distances unless with the most serious losses or waste by the absorption of work of the motor in torsion and friction of the gearing and shaft, and in friction, flexure and slippings of the belt, etc. Until within a few years, toothed gearing, either as spur or bevel wheels, or a combination of both, has been almost universally employed for first motions, the smaller powers being taken off pulleys by leather bands or belts. The facility of taking small powers off pulleys to machines by means of belts, and the absence of noise and vibration, led to the adoption, in the United States of America, of broad leather belts for the transmission of large powers from the prime mover to the shafting in factories; but the mechanical difficulties attending the transmission of large powers by means of large belts, have, for a considerable time, interested mechanical engineers in efforts to find a satisfactory substitute.

"The first systematic attempt to substitute a rope of any kind in place of belts or shafts to transmit power from a mot to machinery at a distance was made by Mr. C. F. Hirr

.

Logleback on the Rhine. The experiments which finally resulted in success extended from 1852 to 1860; for, notwithstanding the apparent simplicity of the proposition, there were serious and unexpected mechanical difficulties to be overcome. It has been said that the gist of this invention is in a very simple principle, viz. the substitution of velocity of motion for mass of matter moved, because a given force may be equally well represented by a heavy body moving slowly or a light body moving swiftly. Thus it may be said he imparted portability to his force, since it may be neither practicable to move the motor to the work nor to transmit its motion through slow-moving heavy shafting."

Hirn Teleodynamic Cable.

The cable employed was of wire about 1 c. m. in diameter, and bearing pulleys were placed about one hundred and fifty yards apart.

The transmission of power by Hirn's Teleodynamic cable has been frequently employed in this country, but cannot be said to have met with a success commensurate with its great promise. This is largely due to the rigidity and great weight of the cable. Its rigidity resists flexure around the terminal pulleys, and its great weight and velocity generate strong centrifugal force as it passes around the pulley to reverse the direction of its motion. Both of these add to the load of the motor.

The use of wire ropes for transmitting power is, practically, limited to long spans, and has not been found to be adapted to take the place of belts. But ropes had long been used to drive small machines and in a large way for cable haulage in mines and on inclined railways. Hemp and cotton ropes have been employed for this purpose in England for several years. The distinguishing feature of the English system is the duplication of individual rope belts when the power to be transmitted

exceeded the capacity of a single rope of convenient size. It is evident the diameter of the rope is an important factor in rope transmission, because in passing around the terminal wheels the effects of flexure are in proportion to the diameter of the rope. In our practice the diameter of the terminal wheels is not less than sixty rope diameters, and the importance, if not the necessity, of small ropes is therefore at once perceptible. Hence when, under the English system, the power to be transmitted exceeds the capacity of one rope belt of convenient size, another rope belt is added, and so on.

English System.

This system has several disadvantages, among which are prominent the impossibility of securing uniform tension on the sev eral ropes, and the multiplicity of splices. Nevertheless it quite extensively used in Europe and the East, but has not be received with equal favor in America. As a matter of the American engineer not being hampered by the conserv

of established custom, has preferred the wide flat belt to the English duplicate round belt; but the modern growth of mechanical science in this country has led to many experiments looking to an avoidance of the cost and mechanical losses attending the wide belt. The outcome of these experiments is the American system of rope transmission, originated by the Dodge Manufacturing Company, of Mishawaka, Ind. It employs but one rope, however many wraps may be required to transmit the given power, and by a system of winders the ropes pass the terminal wheels as many times as may be required to secure complete adhesion and entire avoidance of slip. This invention was patented in 1885, but has been greatly improved since that date and made the subject of several additional patents. Probably the most important is the system of double wind whereby the splice is relieved of one-half the strain to which it might be subjected under the older system by variations of load.

With this brief notice of previous systems of power transmission by means of ropes, I will leave them and confine myself to the American system, which by its practical success in transmitting power over long distances, and in supplanting wide belts for short distances, has earned its title as a distinctive system.

This method of transmitting power depends upon two principles in mechanics :

(1) The dynamic force is measured by the product of the force and the velocity with which it moves.

(2) In mechanical work power may be exchanged for velocity, and velocity for power.

The hidden principle involved in this system may be made plain by the following illustration, taken from Van Nostrand's Science Series

:

"To illustrate, let us suppose a bar of iron, having a cross sectional area of one square inch, to move endlong at the rate of two feet per second. Now, if the resistance overcome is, say, 5,000 pounds, work will be performed at the rate of 10,000 foot-pounds per second. Now, if we double the velocity of the bar, we will transmit twice the amount of work with