252 PHILOSOPHICAL TRANSACTIONS. [aNNO 1751. 



yards of Uieir boats, but cannot strike one, unless it be sleeping, or suckling its 

 young ones. Hence the bad success, and necessity of giving a premium to in- 

 demnify the adventurers. Hence we also see that a machine, which would pro- 

 ject a harpoon 30 yards with sufficient force and proper direction, must give a 

 chance for taking 30 whales for one in the common way. 



Several machines have been proposed to answer this end, but have all proved 

 abortive. The crossbow was tried, but was too weak, and subject to break with 

 the frost in those cold climates. Gunpowder was next applied, it is said with no 

 better success ; for, besides the difficulty of applying it to throw those heavy 

 bodies in the form of darts, especially such as must carry a rope along with them, 

 it frightens all the whales from the place, where it is fired, either by the light, 

 or by the explosion, which it poduces ; perhaps both ways ; but probably more 

 by the sound than the light ; for in the summer time there is in those parts a 

 continual day for several months, so that a flash would not be remarkable. 



The machine which he recommends instead of those, is the ancient Balista, 

 which is accurately described in the 13th chapter of Polybius, translated into 

 French by Mons. Folard, who has nicely distinguished it from the catapulta, 

 with which most of the ancient historians have confounded it, though these ma- 

 chines had distinct offices ; for the catapulta threw vast masses of metal and 

 stone in a parabolic curve, and the balista projected darts, some of 6o lb. weight, 

 in a horizontal direction. The projectile power of both these machines de- 

 pended on twisted ropes, which moved a lever placed in their centre. In the 

 catapulta this lever moved vertically, and threw off globular bodies, as above- 

 mentioned ; but in the balista there were 2 levers, which moved horizontally, 

 and acted like a cross-bow. The force of this machine may be increased to any 

 necessary degree, by multiplying the number of springs or ropes, and increasing 

 the length of the lever, which turns the windlace, that draws back the cross cord, 

 or in other words charges it. It has all necessary motions, and is contrived to 

 stand on a pedestal in the head of a boat. It is so simple, that any person may 

 learn how to use it in a short time; and when once it is successfully applied, we 

 shall be no longer obliged to the instruction of the Dutch, who reckon it their 

 interest to obstruct our success in every useful branch of trade. 



LXXII. An Engine for raising Water by Fire ; being an hnprovement of Sa- 

 verys Construction, to render it capable of working itself, invented by Mr. De 

 Moura of Portugal, F. R. S. described by Mr. J. Smeaton. p. 43(j. 



This engine consists of a receiver, a steam and an injection-cock ; a suction 

 and a forcing-pipe, each furnished with a valve ; with a boiler, which, on ac- 

 count of its bulk and weight, is not sent with the rest ; but, as it may be of the 

 common globular shape, and having nothing particular in its construction, a de- 



