12 
HISTORY OF THE INVENTION. 
The results of these trials were so satisfactory as to lead to the formation of 
a Company under the title of “ The Ship Propeller Company.” The system of 
propulsion was, however, so unpopular among manufacturing engineers and 
scientific men generally, that it was some time before a manufacturer could 
be found to undertake an order to construct the engines and machinery for a 
large experimental vessel. Messrs. George and John Rennie (sons of the cele 
brated Mr. John Rennie) having, however, witnessed several trials with the little 
experimental vessel, and satisfied themselves that the invention was one of con 
siderable promise, not only undertook the order, but contributed largely towards 
the necessary funds for carrying out the designs of the Company. It may be 
interesting to state that an invention which has been so far established that it has 
now become a subject of honourable competition to discover and apply the best 
arrangement of machinery and form of propeller, was, at that period, alluded to 
with ridicule, or at best with expressions of regret that Messrs. Rennie should 
sport with their reputation and a Company with their capital in so hopeless a 
project. Such facts as these cannot be considered unworthy of notice, as showing 
the vast difficulties which oppose the prosecution of a new discovery, and as proving 
that the successful practical application of a mechanical invention is attended 
with as many obstacles, and requires the possession of a quality of mind, almost 
as rare and as valuable to the community as the highest powers of invention. 
The screw propeller was at last carried into effect by constructing a vessel called 
the Archimedes, of the following dimensions: 
Extreme length 
Length between perpendiculars 
Extreme breadth 
Depth of hold 
Draught of water aft 
Draught of water forward 
Burden .... 
United power of engines . 
125 feet. 
106 feet 8 inches. 
21 feet 10 inches. 
13 feet. 
10 feet. 
9 feet. 
232 tons. 
80 horses. 
The engines and machinery were constructed, as we have stated, by Messrs. 
Rennie. The figures in the copper-plate represent an elevation and plan of the 
engines, and of the whole of the machinery, excepting the boilers. 
The cylinders, instead of being placed transversely in the vessel, as in the case 
of vessels fitted with paddles, are placed fore and aft, or at a right angle to the 
ordinary position. They are of the kind called direct engines, that is to say, 
the motion is communicated from the engines to the cranks by the direct action 
of the connecting rods, instead of being transmitted by levers. There is but 
one air pump to both engines, which is worked by the intermediate shaft being