268 
Mr Sears, On the Longitudinal Impact 
by means of which coarse adjustments were effected. Fine 
adjustments were made by raising or lowering the blocks, B, by 
means of the screws, C. The regulators could easily be fixed at 
any point along the wooden beams by first wedging the bevelled 
edge, D, under the guide, F, and then pressing home the sharp 
pins, E. At their lower ends the suspending cords were attached 
to the rods by small loops, which passed over little hooks screwed 
into the rods ( A , Fig. 4). In order to get the axes of the rods 
collinear, four long threads of cotton ( C , Fig. 2 A) were stretched 
between two brass plates, E , in a vertical plane midway between 
the two beams, and the rods so adjusted as to lie just in between 
them without touching any of them. As a matter of fact it was 
found that, when the rods had been nearly adjusted in this way, 
the best test of axial collinearity was the complete absence of the 
note due to the transversal vibrations of the rods, when they were 
allowed to impinge. The note due to the longitudinal vibrations, 
being much higher than this, was easily distinguishable from it, 
and, moreover, so little energy was taken up in longitudinal 
vibrations (the two rods being equal), that very little “ ring ” was 
associated with this form. 
