These three ropes are conveying not less than 286 horse power or an average of 95 horse power per rope instead of only 25.4 horse power as stated in the tables mentioned.

That the ropes on this particular drive were not overworked was clearly demonstrated by successfully driving the whole of the load with two ropes for the greater part of a day, and that without any evidence of slip, on account of the third having to be laid aside for repairs due to an accident. This represents 143 horse power per rope.

A recent report from the engineer in charge of a similar drive in Scotland suggests an easy transmission of 100 horse power for 11⁄2 inch ropes at 7,000 feet, and also volunteers the opinion based upon a wide experience of rope-driven engines, that at this velocity ropes will last quite as long as when running at 5,000 feet.

I have emphasized this phase of the rope driving question because of the persistency with which tables, figuring upon these theoretical deductions, make their annual appearance, in pocketbook diaries, and other engineering guides, notwithstanding the foregoing and other procurable evidence to the contrary.

We are persuaded, therefore, that the absence of tabulated figures giving the powers between medium and high velocities, justifies our contention that we are erring, if anything, on the side of safety by publishing a table that presumes upon a constantly increasing power in the ratio of advancing speed to the utmost limit of mechanical endurance. See pages 362 and 363.

OVER ROPING.

While allowing a fair margin of safety in making calculations for power, it should be remembered that there is such a thing. as over roping to the detriment of efficiency. Resistance from this cause is not, however, very pronounced in the steady going drives of textile factories, where the fault is mostly displayed by the tendency of the "idle" to exchange with the working side of the ropes.

In the driving of iron rolling mills, subject as it is to enormous

TABLE OF HORSE POWERS,

This implies a consistent loss of power on the entire range, and evidently means increasing the percentage of friction as the load decreases, that is, when catering for the maximum quantity.

For this interesting demonstration we are indebted to Mr. J. INGHAM, of Bolton, who has successfully negotiated a large number of sheet and tinplate rolling mill drives.

When discussing a paper read February, 1912, at Newcastle, by Mr. C. A. ABLETT, B. Sc., on "Some General Principles Involved in the Electrical Driving of Rolling Mills," Mr. INGHAM very ably contested the high friction rates of 10 per cent. attributed to ropes by the writer of the paper, and showed how that by fixing the rope design at from So per cent. to 90 per