VIII. MACHINERY. 477 



2073. Apparatus for supposed Perpetual Motion, used by 

 Dr. Thomas Young. The Royal Institution of Great Britain. 



A wheel supposed to be capable of producing a perpetual motion, the 

 descending balls acting at a greater distance from the centre, but being fewer 

 in number than the ascending ones. "Lectures on Natural Philosophy," 

 by Thomas Young, M.D., 1807. 



2074. Model of Parallel Motion, consisting of three parts 

 only. William Hayden. 



This parallel motion depends on the properties of a right-angled triangle 

 where the sides are as 3, 4, and 5. The longer radial arm being the less of 

 the two sides containing the right angle, and the shorter radial arm half the 

 longer of such sides, while the side of the triangle connecting the arms corre- 

 sponds to the remaining half of such longer side. The distance between the 

 fixed centres corresponds to the longest side of the triangle. 



The line of motion is perpendicular to the straight line joining the fixed 

 centres, and on the centre of the shorter radial arm ; it is limited by the 

 motion of the less radial arm through the less of the acute angles of the 

 triangle first before referred to. The point giving the parallel motion is found 

 by drawing a perpendicular from one of the acute angles of an isosceles 

 triangle, where each of the equal sides is to the base as 5 to 8 (the other 

 acute angle and the obtuse angle being connected to the two radial arms), to 

 the perpendicular on the centre of the less radial arm. 



2075. Parallel Motion ; invented by the late Richard Roberts, 

 C.E., Manchester ; the peculiarity consists in the fixed centres 

 being in the plane of the parallelism. 



The Committee, Royal Museum, Peel Park, Salford. 



2076. McKay's patent Equilibrium Drilling Tools, with 

 specimens of work. Menzies fy Blagburn. 



This apparatus is designed to permit circular holes of any size to be bored 

 out with mathematical accuracy and absolute precision as to their relative 

 positions. 



This object is attained by maintaining the centre point, around which the 

 cutters revolve, immovably fixed during the process of boring, while the 

 cutters are advanced, and are held in equilibrium with the centre points by a 

 hydraulic medium contained within the chambers of the tool, the pressure 

 being conveyed by the action of the feed given to the boring machine. 



This apparatus is exhibited for the purpose of showing how accurate work 

 can be obtained with a minimum of skilled labour and cost. 



Machine for drilling Watch Frames. 



H.M. Commissioners of Patents, 



2O76a. Isometric Drawing of an Expanding Mandril, 



or tool for fixing the tubes in the plates of boilers by expanding 

 the ends so that the tubes are firmly fixed in their places. 



W. H. Prosser. 



Invented and made by the late Richard Prosser of Birmingham in 1845. 

 Two of these expanders were sent to the United States in 1 847 ; an im- 

 provement on them is now being imported from that country. 



