Mechanical Science. 137 



2. Hydraulic Instrument for raising Water. — It is well known 

 that if a glass vessel containing water be placed in the centre 

 of a whirling table, the water, by the centrifugal force, will be 

 thrown from the centre outwardly, and the surface of the water 

 will assume a form approaching to that of a parabola. 



Dr, Crelle, architect to the King of Prussia, has accordingly 

 made the bent tube in his model of the improved Hessian 

 machine of a parabolic shape, and on being placed in a certain 

 depth of water, the water entering below at a hole in the centre 

 of the tube, is by the quick whirling movement given to the 

 machine, raised and delivered at the upper ends of the tube 

 into the circular trough, and runs out from thence at a 

 spout on one side of it. Many tubes may be thus combined, 

 and the quantity of water raised be increased accordingly. 

 The value of this machine on a large scale is not known, but 

 certainly this is the best form of it. — Tech. Rep. iii. 99. 



3. Hydroparabolic Mirror — standard Measure. — Mr. Busby, 

 well known as the constructor of a hydraulic orrery, applies 

 the syphon as a generator of rotary motion. A floating circular 

 vessel is placed in a reservoir of water, and has a syphon 

 attached to it, one leg of the syphon dips into the water of 

 the reservoir, the other passes over the side of the reservoir to 

 a lower level than the water within, and discharging a minute 

 stream by a lateral aperture, gives to the floating vessel a 

 perfectly equable revolving motion. By means of it, INIr. Busby 

 says he has produced a perfect hydroparabolic mirror fifty-four 

 inches in diameter, thus being able to create any magnifying 

 power ad libitum. He refers to it also as a means of obtaining 

 an universal standard of measure. Thus, a given parabolic 

 speculum will invariably be formed by any given rotation at 

 any known level and latitude, and the focal distance of any 

 parabola must under those circumstances be always a given 

 dimension. — Tran. Soc. Arts, xl. 



4. Feeding of Engine Boilers. — Thomas Hall, engineman to 

 the GlasgiOw Water Company, having remarked the waste of 

 fuel which occurred at those times when a steam-engine stopped 

 working, as at nipht, &c., was induced to alter his mode of 

 feeding the boilers with water, with a view to prevent as much 

 of this waste as possible. Instead of letting in a continual sup- 

 ply of water, equal to the portion converted into vapour, he 

 took every opportunity, when the engiue was stopped for a 



