{HEAD ~ a variable weight loading device} carried by {TAIL ~ said carriage} for loading the sample holder such that a selected load can be applied to the sample normal to the friction surface, said variable weight loading device including a weight platform on which removable weights can be stacked and removed to selectively vary the load applied to the sample 
{ HEAD ~ a variable weight loading device } carried by { TAIL ~ said carriage } for loading the sample holder such that a selected load can be applied to the sample normal to the friction surface , said variable weight loading device including a weight platform on which removable weights can be stacked and removed to selectively vary the load applied to the sample
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH