MECHANICS AND USEFUL ARTS. 69 



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in the sides of the external cylinder, the air is drawn through one opening 

 and expelled through the other, whatever may be the degree of resistance 

 interposed. 



The fixed cylinder or external case of a blower at Hoe's foundry, in New 

 York, is forty inches in diameter, and thirty-six inches long. The internal 

 cylinder is thirty inches in diameter, and carries three wings of half-inch 

 boiler iron. The centre on which the internal cylinder revolves is five 

 inches from the true centre of the case, and the surfaces, consequently, are in 

 contact at one point, while on the opposite side they are ten niches apart. 

 The protrusion and withdrawal of the wings is performed by a very simple 

 device, in which consists the chief novelty of the invention as compared with 

 other winged rotary devices. The inner cylinder is penetrated by a fixed 

 shaft, which shaft is bent to one side after passing through the end until it 

 coincides with the centre of the large cylinder or outer case. To this portion 

 of the fixed shaft the wings are connected, and their extremities are thus 

 made to travel hi a perfect circle in close contact with the inside of the outer 

 case. The inner cylinder thus gives motion to the wings, and in every revo- 

 lution its periphery is slid outward and again contracted upon them. It is 

 not strictly true that the wings are thrust outward and withdrawn, although 

 it is so relatively to the inner cylinder. The passage of the wings through 

 the latter is packed in a very ingenious and perfect manner, to allow for the 

 varying angle which it continually assumes, and the whole machine appears 

 to involve but a moderate degree of cost, either for construction or repairs. 

 The inlet and outlet openings are made, of course, near the point where the 

 two cylindric surfaces are in contact ; and the blast of" wind is very nearly 

 steady and continuous, a slight fluctuation of pressure occurring with the 

 commencement of each wing to cross the delivery opening. This fluctuation 

 is due to the regurgitation or back flow of the air until the space between the 

 wings is compressed to the extent required for delivery. The air in the 

 blower at Hoe's is compressed to about one pound plus of pressure, and the 

 variation alluded to in the intensity of the blast, is too slight to be any annoy- 

 ance. The blower described is driven about seventy-five turns per minute, 

 and requires only from one-fifth to one quarter the power formerly consumed 

 in obtaining the same effect from a very large and well constructed fan. 



Cooper's Improved Blast Pipe. Mr. "W. E. Cooper, of Dunkirk, N. Y.. has 

 introduced a form of blast nozzle which has been applied to several engines 

 on the Xew York and Erie Kailroad with great success. It has heretofore 

 been common to discharge the steam into the chimney through a round 

 opening. Mr. C. simply forms it into a ring or annular passage, so that the 

 escaping current presents a great surface both on its exterior and ulterior 

 sides to act on the smoke and drag it up the chimney. 



IMPROVEMENTS IX GEARINGS AND BEARINGS. 



New Factional Gearing. Where high speed and little force are required in 

 transmitting power from one wheel to another it is common to provide no 

 teeth, but simply to let their smooth surfaces rub together. A Mr. James 

 Robertson has lately introduced in Scotland a " grooved surface frictional 



