202 On Mr. Horn's Theory of Vision. 



at times when other ships cannot ; of towing vessels in rivers, 

 and a variety of other useful occupations. Neither, from their ex- 

 tra length and breadth, would they pitch or roll so much. A 

 sail might be occasionally used in lieu of the engine to save fuel. 



XIII. It would follow from the last premises, that in action 

 their guns might be pointed with more precision, and the heeling 

 after firing would be less. 



XIV. The objections to the employment of steam-boats or 

 barges in canals, is the destruction occasioned to their banks by 

 the violent action of the water during the ])assage of the steam- 

 boats, and to the want of width in the locks. Would these ob- 

 jections be partly remedied by placing the paddles behind ? (for 

 we have all along supposed paddles the best) or could any of 

 the modes hitherto practised for propelling boats answer ; so 

 as to be of use in doing away with the number of horses and 

 men usually employed in this service ? 



XV. Would not the advantages attending a steam-boat, solely 

 for the purpose of towing other boats with passengers and goods, 

 be superior to the present mode, of having the passengers and 

 goods in the same boat as the engine, thereby rendering the 

 vessel weaker by its great length, and unequally strained by the 

 greater or less weight of passengers and goods, which is always 

 liable to vary, and must sink the vessel more or less ; thus drown- 

 ing her wheels or paddles, and consequently obstructing her mo- 

 tion? — independent of those dreadful accidents, frequently liable 

 to arise from bad engines, as lately in America, and one instance 

 in this country. 



XVI. Lastly, and politically speaking, are the benefits hereto- 

 fore stated, as liable to occur by the employment of steam- 

 vessels in war, in navigation and commerce, by defeating our 

 enemies abroad, by facihtating conveyance at home, and ren- 

 dering cheaper the commodities of foreign coimtries, to be 

 counterbalanced by consuming with additional extravagance the 

 very vitals of our country (which our coals are) by the great ca- 

 pital consumed in the rapid destruction of the materials of which 

 steam-vessels are composed ; and by creating a superabundant 

 population, which have been, still are, and probably will be, the 

 curse of this great and hitherto happy country ? G. R. 



LI. On Mr. Horn's Theory of Vision. 



To Mr. Tilloch. 



Sir, — i OUR correspondent J. Q. R. not having seen " TAe 

 Seat of Vision determined," has unconsciously attributed some 



inconsistencies 



