184 SCIOPTICON MANUAL. 



" On either side of the tube d, and as near as convenient, 

 are placed two eye-bolts, from which are carried wire cords 

 //, up to and over the pulleys g g. After passing these 

 pulleys or shrives a few inches (the holder being at its 

 lowest point), the ends of the cords are inserted and fastened 

 in holes in the crossbar h, as shown in Fig. 2, p. 183. 

 Midway between these cords is inserted, from the opposite 

 side of the crossbar, a single cord, as is also shown in Fig. 2, 

 p. 183, as well as in Fig. 51, which represents this portion 

 broken off and swinging around at a right angle to its proper 

 position. This cord i passes over the shrive k, and extends 

 down to within a convenient distance of the floor, and has 

 attached to its extremity the pan /, for holding the weight 

 shown in Fig. 3, p. 183. Care must be taken that the dis- 

 tance of the shrive Tc from the crossbar h, and also from the 

 bottom of the scale pan to the floor, is as great as the proposed 

 rise and fall of the holder. The arrangement of cords, shrives, 

 etc., will be readily seen in the perspective view, Fig. 51. 



" The pipe for the admission and exit of the gas is shown 

 as passing through the side of the wooden tank, and rising 

 near the centre, to within a few inches of the top of the holder. 



" The manner of using is as follows : The cock o, in the 

 inlet pipe, being open to the atmosphere, water is admitted 

 to the tank until it rises a little above the lower edge of the 

 top of the holder, when the cock should be closed. Weights 

 (Fig. 3, p. 183) are placed on scale pan I, in sufficient 

 amount to overbalance the weight of the holder, and to 

 overcome the friction of the cords and pulleys. Communi- 

 cation being opened between the inlet pipe and the source 

 of gas supply, the gas enters, and the holder rises until filled. 

 The supply of gas should then be cut off, the weights re- 

 moved from the pan I, the space at the top of the holder 

 filled with water, and the gas is ready for use, under the 

 necessary pressure. When the holder is exhausted, the 



