666 The Earl of Berkeley on a 



two elevations under A in fig. 2) slide on either end of 

 the short arms of the T's and hold a Chesterman steel ruler 

 (1*5 metres long, 5*7 cm. wide, and 2'4 mm. thick) in the 

 jaws* B of fig. 2. The pins Ff (plan and elevation under D 

 of fig. 2) slide on the long arms of the T's; they are pulled 



Fig". 2. 



A 



E«-$p 



J 





c 



$- 



-M--& 





/^S-^ 









v-lisX? -"-v ; ' 





VSS^^^, 



y*- 



- "® Tgr 



2 3 4 SOW. 



Steel ball 



towards each other by the cord G which passes round the 

 grooves D of fig. 2 — this cord is "belayed - " by pulling it 

 tight into a V-shaped slot cut at H in the brass right-angled 

 piece J. 



* It may be of use to mention that these jaws were made by putting 

 two saw cuts, with a circular saw, through the solid pin at right angles 

 to one another and parallel to the vertical axis. 



t In actual construction the T with the longer arm has that arm set 

 high so as to clear the other T should it be necessary for them to cross — 

 hence one of the pins is made longer so as to avoid " wringing " the ruler. 



