[ 200 ] 

 L. Queries on Steam-Boats. By Mr. George Rennie. 



To Mr. Tdlocli. 



Sir, — W KOEVKR reflects on the numerous improvements In 

 the arts and sciences, to vvhicli a sliort but eventful period has 

 given birth, cannot but hail with pleasure the recent introduction 

 of steam-vessels, — an improvement of the highest importance, 

 which discloses a new sera in navigation, and demands every effort 

 for its further improvement. I have therefore sent the follow- 

 ing queries in reference to this interesting subject; trusting that 

 such of your readers as may deem an inquiry of this nature in- 

 teresting, will turn their scientific talents to its further elucida- 

 tion, which I will also endeavour to do, should not other avoca- 

 tions intervene to prevent me. 



I have the honour to be, sir. 



Yours, &c. 

 London, March 12, 1817. GkoRGE ReNNIE. 



I. Steam-vessels (unlike ships, whose velocity is always irre- 

 gular and varied at every augmentation or diminution of the 

 wind) have one assigned velocity, according to their respective 

 propelling powers. What is the best form that ouglit to be 

 given to the head and stern ? The extreme length, breadth and 

 depth ? VVhetlier flat or round bottom, in order tliat the requi- 

 sites of stability, velocity and strength, may attain a minimum? 



II. It has been found that the ratio of the resistance being 

 as the squares of the velocities (especially in large surfaces and 

 great velocities) does not maintain ; or, in other words, that an 

 engine of a quadruple power will not produce a double effect or 

 velocity:— -can anyfornnda be adapted to practice so as to include 

 the circumstances of friction, imperfect fluidity, or adhesion ? 



III. From the experiments of Dubuat, it is deduced that the 

 whole impulse to be withstood or overcome by the external f;>rce 

 is the sum of the plus and minus pressures and of friction ; that 

 the non-pressure on the hinder part was prodigiously diminished 

 (l-4th), tiy making the length of the body triple its breadth; from 

 which he infers that the lengthening of a ship diiuiiiihhes the 

 resistance ; — a paradox, for it supposes a less power to dis])lace 

 •A greater quantity of fluid than a small cjuantity, independent of 

 other circumstances. How far is this consistent with theory 

 and practice ? 



IV. Admitting perfection to the steam, — to which Mr. Watt 

 to his everlasting credit has been so instriuncntal; — how far con- 

 sistent with oeconomy, saving of fuel, and attendance on two 



furnaces. 



