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power draught, draught power

[This phrase, of course, has many meanings other than the one below, having to do with shortages of electricity, employment of sports players, forced ventilation, and so on. One kind of occurrence, however, needs to be distinguished from the meaning below. In a judgment of the Indian Supreme Court in the Cow Slaughter Case (Civil Appeals Nos. 4937-40 of 1998 with Nos. 4941-45 of 1998, decided on 26 October 2005) we read

The aged bullocks i.e. above 16 years age generated 0.68 horse power draft output per bullock while the prime bullock generated 0.83 horse power per bullock during carting/hauling draft work in a summer with about more than 42°C temp.

The insertion of the word “horse,” even with the space before power, shows this is simply horsepower, a unit of power, in the service of draft, and not the unit of force described below.]

In Scotland, a unit of force used to characterize the size of a object being towed (e.g., dead whales), = the force exerted by a team containing that number of oxen, probably something around 410 newtons per ox.

In a respected publication¹ of 1861, one reads,

By the leges forestarum, § 17, all whales thrown ashore, of above six power draught, belong to the Queen; but in practice they require to be of greater size before they become her Majesty's property, or that of the admiral, her donatory.

In a law journal² of 1903:

According to the Leges Forestarum, c. 17 (i), all whales thrown ashore, of above six draught power, belonged to the King.

(i) Erskine's Inst. II. i. 10. We have only Erskine's authority that this rule is contained in the Leges Forestarum. No extant copy contains this provision.

Both authors cite Erskine, and in Erskine³ we find:

By the Leges Forestarum, § 17, according to a copy preserved in the Advocates' library, all great whales belong to the King, and also such small whales as may not be drawn from the water to the nearest part of the land on a wain with six oxen.

According to Cotterell and Kamminga⁴, a bullock exerts a force of 410 newtons. If we make the dangerous assumption that the force exerted by a team is a simple multiple of that of an individual ox, 6 draught power would be about 2400 newtons.

1. William Bell.
A Dictionary and Digest of the Law of Scotland, with Short Explanations of the Most Ordinary English Law Terms.
With corrections and additions by George Ross.
Edinburgh: Bell and Bradfute, 1861.

Page 859, under the heading: “Whales.”

2. William Trotter.
Property in Wild Animals.
The Juridical Review. Volume 15, pages 138 - 154 (1903).

Page 152.
The most recent edition of the forest law, very carefully edited with both the Latin and an English translation (pages 304-307), says nothing about whales:
J. Gilbert.
Hunting and Hunting Reserves in Medieval Scotland.
Edinburgh: John Donald, 1979.

3. John Erskine.
An Institute of the Law of Scotland, in Four Books, in the order of Sir George Mackenzie's Institutions of that Law. Volume I.
A new edition edited by James Ivory.
Edinburgh: Bell and Bradfute, 1824.

Page 223.

4. Brian Cotterell and John Kamminga.
Mechanics of Pre-industrial Technology.
Cambridge (UK): Cambridge University Press, 1990.

Table 2.5, page 38. Their source is W. J. M. Rankine, Useful rules and tables (1889).