avowed intention of applying a similar principle of 

 construction to the building of fast-sailing iron steam- 

 boats." This intimation, in 1829, to the since famous 

 Glasgow iron-ship builders, that they could not claim 

 the invention because Trevithick had made such a boat 

 in 1827, was probably in ignorance of Trevithick's patent 

 and models of 1809, 1 explaining the advantages of ships 

 of iron, either under sail or under steam, for commerce 

 or for fighting-ships. The improved high-pressure 

 steam-engine then in hand for iron ships was but the 

 perfecting of his plans of twenty years before. 2 



" LAUDERDALE HOUSE, HIGHGATE, April 19th, 1830. 

 " MR. GILBERT, 



" Sir, I find by looking into the ' Art of Gunnery ' that 

 a 42-lb. shot discharged at the rate of 2000 feet a second in 

 vacuum would send it to the height of 63,360 feet, which 

 multiplied by the weight of the shot would be 2,661,120 Ib?., 

 with 12 Ibs. of powder ; and as guns, after being heated to about 

 the heat of boiling water, will recoil their usual distance with 

 half their first charge of pow ? der, it proves that one-half the 

 powder at first is lost in heating the gun to about 212 D , which 

 is a great deal under the heat of fired powder, therefore only 

 6 Ibs. of powder effective force is applied to the ball. Now 

 suppose this 6 Ibs. of powder to be one quarter part carbon, 

 1^ Ib. is all the heat that can possibly be applied to perform 

 this duty ; then 1 Ib. of carbon would be equal to 1,774,080 Ibs. 

 of duty actually performed; but if you take into calculation 

 the great loss of power by the powder not being instantly all 

 set on fire, w itk the gun so much below the heat of fired powder, 

 the windage by the sides of the shot, the ball flying from the 

 powder, and the immense power remaining in the gun at 

 the time of the ball leaving its muzzle ; if this was applied 

 expansively, as in a cylinder, it may fairly be said to have 

 double this power, or 3,548,160 Ibs. for 1 Ib. of carbon con- 

 sumed, which, multiplied by 84, being the pounds in 1 bushel 



1 <-.',> 



Sec vol. i., p. .'Joi'. - Scr vol. i., p. :Ji".. 



