Weiss resembled those of the tomcat aforesaid and invited an analogous reply. To a responsible professional man his extraordinary precautions were at once an affront and a challenge. Apart from graver considerations, I found myself dwelling with unholy pleasure on the prospect of locating the secret hiding-place from which he seemed to grin at me with such complacent defiance; and I lost no time and spared no trouble in preparing myself for the adventure. The very hansom which bore me from the Temple to Kennington Lane was utilized for a preliminary test of Thorndyke’s little apparatus. During the whole of that brief journey I watched the compass closely, noted the feel and sound of the road-material and timed the trotting of the horse. And the result was quite encouraging. It is true that the compass-needle oscillated wildly to the vibration of the cab, but still its oscillations took place around a definite point which was the average direction, and it was evident to me that the data it furnished were very fairly reliable. I felt very little doubt, after the preliminary trial, as to my being able to produce a moderately intelligible track-chart if only I should get an opportunity to exercise my skill.