To determine the prevalence of this relative sensitiveness to heat of the right and left hand, the test ought to be applied to uncultured and savage, as well as to civilised man. The elements which tend to complicate the inquiry are very various. The left-handed man is nearly always ambidextrous, though with an instinctive preference for the left hand in any operation requiring either special dexterity or unusual force. Hence his right hand, though less in use than that of the right-handed man, is in no such condition of habitual inertia as the other’s left hand. Again, a large number give the preference to the right hand from a mere compliance with the practice of the majority; but with no special innate impulse to the use of one hand rather than the other. But besides those, there is a considerable minority in whom certain indications suffice to show that the bias, though no strong and overruling impulse, is in favour of the left hand. I have, accordingly, had a series of tentative observations made for me in the Physical Laboratory of the University of Toronto, under the superintendence of Mr. W. J. Loudon, Demonstrator of Physics. The undergraduates willingly submitted themselves to the requisite tests; and the series of experiments were carried out by Mr. Loudon with the utmost care. No idea was allowed to transpire calculated to suggest anticipated results. A highly characteristic Canadian test of any latent tendency to right or left-handedness was employed. In the use of the axe, so familiar to nearly every Canadian, alike in summer camping-out and in the preparation of winter fuel, the instinctive preference for one or other hand is shown in always keeping the surer hand nearest the axe-blade. This test was the one appealed to in classifying those who submitted to the following experiments. The trial was made with water very nearly 30° centigrade. The results arrived at are shown here, the persons experimented on being divided into three classes: (1) Right-handed, or those who habitually use the right hand, and who in handling an axe place the right hand above the left, nearest the axe-head. (2) Ordinarily using the right hand, but placing the left hand above the right in the use of the axe. These appear to be generally ambidextrous. (3) Those who are generally said to be left-handed, but employ the pen in the right hand, and also use that hand in many other operations. This class includes very varying degrees of bias; and though loosely characterised as left-handed, from some greater or less tendency to use that hand, the majority of them were found to place the right hand above the left in the use of the axe. One hundred and sixty-four in all were subjected to the test, with the following results: Of ninety right-handed persons, thirty-five found the right hand the more sensitive, thirty-three the left hand, and twenty-two failed to discern an appreciable difference. Of fifty-six