20 DB. A. E. H. TUTTON: 



transverse motion, or both, and which involves certain mechanical novelties, may also 

 be given. The bar carriage is composed of three essential parts, all of the same cast 

 iron as the V-and-plane beds, namely, (a) a lower part, the main carriage, P, 2 feet 

 1 inch long, 5^ inches wide, and 2f inches deep to the bottom of the V, and which is 

 the longitudinal slider on the V-and-plane bed , (b) an intermediate part, Q, 3 feet 

 6 inches long, 3f inches wide, and 1^ inches thick, which is capable of transverse 

 motion over (a) ; and (c) the upper table v already alluded to in (6), of equal length 

 and width to (b), and lyg- inches thick, for the support of the standard bars Bj and B 2 ; 

 this part (c) may be either of the three interchangeable table tops specified in (6). 



The main carriage, P, slides on the lower V-and-plane bed, by hand as regards 

 its coarse adjustment for position, but as respects its fine adjustment by means 

 of a pair of pushing pistons shown only in fig. 1, and which form a novel feature. 

 Each of these fine-adjusting pistons, 3 inches in length, is carried by a slider-block 

 of similar section to the bar carriage, but only 5 inches long, and which may be 

 locked to the bed in any position by the same T-bolt stud device, worked by a 

 projecting lever, which is common to all the sliding blocks traversing both the upper 

 and the lower V-and-plane beds, the stud fitting the T-groove in the bed in each 

 case. The fine movement is effected by rotation of a relatively large gunmetal wheel 

 facing the observer, which carries at the inner end of its transverse shaft a bevel 

 wheel gearing with another on a short longitudinal shaft, which is really the mother- 

 nut of the central fine screw, whose .smooth outer projecting part (about 1 inch long), 

 with spherically rounded end, is the pushing piston. Where the contact with the 

 piston end occurs the carriage end is faced witli a hardened steel plate. 



The transverse motion is also novel. A cylindrical shaft runs the whole length of 

 the main lower carriage, P, being let into a central channel. In the middle of the 

 shaft a racked quadrant is fixed, which is operated from the front of the carriage 

 facing the observer by means of another large gunmetal wheel, W, which forms the 

 head of an endless screw gearing with the toothed quadrant. Rotation of the wheel 

 rotates the quadrant together with its attached shaft for about 60-degrees. Near the 

 two ends of the shaft are fitted a pair of " tappits," or mechanical fingers ; these are 

 furnished with hardened and somewhat expanded spherical ends, which engage in 

 slots in the under side of the intermediate transversely movable carriage, Q, these 

 slots ^ being lined with hardened steel. Each tappit is thus capable of exerting a 

 pushing force in either direction in order to move the intermediate movable carriage 

 transversely backwards or forwards, according to the direction of rotation of the 

 wheel. Absolutely correct and perfectly smooth motion is obtained by two transverse 

 V-shdes, one near each end precisely at the symmetrical points demanded by AIKY'S 

 well-known formula 



d = 



where d = the distance between the supports, I = the length of the bar (in this case 



