1976] Robinson & Smythe — Behaviour of Small Animals 21 1 
the degree of engineering sophistication that is available. Two 
methods are shown in Figure 1; many others are perfectly feasible. 
The length of the rod determines the extent of the coarse focussing 
that is made possible by simply sliding the microscope assembly 
along the rod before using the rack-and-pinion focussing of the 
subassembly. Unwelcome vibrations may occur if too long a rod 
is used. 
1 , 2 and 3. *arrowed: focussing facilities. 1 . Focussing available on camera focus- 
sing rail (F). 2. Focussing available on microscope mounting rod (R); this is obtained 
by slackening knob (k) that normally attaches microscope to its stand. 3. Focussing 
available by rack-and-pinion focussing of microscope subunit (M). 
Two methods of mounting microscope carrying rod to tripod are shown. In main 
diagram, R is bent at right angles and the starred end is drilled and tapped to take the 
standard camera attachment bolt on the focussing rail at Fc. The detail below shows 
an alternative: R', a straight rod, is drilled and tapped to attach to a ball-and-socket 
camera mount (h) that attaches at Fc. 
