Research Laboratory of the Boyal College of PJtysiclans. 525 



which a cone covered with leather is attached to the loose 

 wheel ; the fixed wheel is bored and lined with leather to 

 receive this cone. 



Another form of clutch designed for me by Mr James 

 Eitchie, Jim., of Edinburgh, is one in which there is a fast drum 

 (a) grooved to carry the cord running from the shaft (Fig. 5). 

 Running on the spindle to which this drum is fixed, is a 

 loose three-speed cone pulley (h) with a groove and clutch (c). 

 Between the loose pulley and the fixed drum is a friction 

 clutch consisting of three straight pieces of metal, which 

 when out of gear are so arranged as to form a small arc of a 

 circle. By pushing in the middle one of these the arc is 

 straightened out, and the outer extremities of the two end 

 pieces are pressed into a groove running round the inside of 

 the fixed drum. In order to fix the clutch, the centre piece 

 is simply made to pass the perpendicular ; there is no spring 

 except that in the metal of the rim of the drum. The clutch 

 never fails, works noiselessly and without the slightest loss 

 of time. 



Electrical, time-marking, and other apparatus, tuning-forks, 

 perfusion apparatus, shunts, compensators, etc., constitute 

 the greater part of the instruments in this room. Marriott's 

 arrangement for obtaining regular pressure for injecting and 

 other purposes, is hung from the roof at two ptoints. 



At each window table on the west side is a bell jar, used 

 for protecting the microscope from dust. This is counter- 

 balanced by a weight which runs on a brass guiding-rod, so 

 that there is no danger of breakage to the window through 

 swinging of the weight. When not in use the bell jar is 

 drawn up out of the way towards the ceiling. Such an 

 arrangement economises room and prevents breakages. 



On each microscope table, which is painted black and 

 hard varnished, a white band about four inches broad is 

 painted, four inches from the edge of the table. Some of 

 the tables instead of being varnished are covered with plate 

 glass, painted as above on the under surface, and embedded 

 in felt. On these glass-covered tables the microscope stands 

 on a felt circle, to diminish the risk of breakaoe when the 

 bell jar is lowered over the microscope. 



