'793* on the study of natiirai history. 315 



the stages moved slower than usual, and inquired 

 th6 reason of it. 



The boatman informed them, that it had been a 

 dry season, and that the water was low in the ca- 

 nal. Upon this he was alked if the water was so 

 low that the boat touched the muddy bottom of the 

 canal ? to which he answered in the negative, ad- 

 ding, (however,)that the dinteicuce in the quantity 

 of water was sufficient co render the draught more 

 difficult to the horse. Dr Franklin struck with this 

 circumstance, and imputing it to the increased re- 

 sistance of the under keel-water by the small foom 

 left for its being displaced by the volume of the 

 boat, ascertained by many well concerted experiments, 

 that if lour men or horses be required to draw a 

 boat in deep water, four leagues in four hours, five 

 will be necefsary to draw the boat the same distance 

 in the same time in (hallow water; a discovery of 

 high importance in the construction of navigable ca- 

 nals, owing to the judicious curiosity of a traveller. 

 One instance more I will give you before I put a 

 final close to this unmerciful letter. 



A playful boy, whose businefs it was to open and 

 close alternately the communication in a steam, 

 or what is commonly called a fire engine, between 

 the boiler and the cylinder, discovered that this 

 trouble might be easily saved. Whenever there- 

 fore he wiQied to be at liberty to divert himself 

 with his companions, he tied a strmg from the 

 handle of the valve which formed a communication 

 to the other part of the machine- that was in moti- 

 ©a ; and the valve then performed its o.^ce without 



