28 On Definitions. 



The alleged advantages of dark clothing during cold weather, thus 

 seem to have been too hastily inferred ; and it appears that, provided 

 the person is not exposed to the sun, the particular color of the cloth- 

 ing is not of real inriportance. 



If color is not a determining quality, neither does roughness appear 

 to be so, for though generally the smooth surfaces aVe lower on the 

 list, this is not universal. The rough suljjhate of baryta is lower on 

 the list than the smooth carbonate of lead. Plumbago occupies alow 

 place, and India ink a comparatively high one. 



The best radiators do not appear to belong to any particular clas3 

 of bodies ; litmus blue and Prussian blue are side by side, while sul- 

 phuret of lead, and the bi-sulphuret of tin, are fifteen numbers apart. 



If the results be admitted as decisive of the radiating powers of the 

 bodies used, they show that each substance has a specific power not 

 depending upon chemical composition, nor upon color. I do not 

 claim to found such a conclusion upon the experiments ; their ob- 

 ject has been before stated, and if they prevent the introduction of an 

 inference from an imperfect induction, as a law of science, the labor 

 bestowed upon them will be amply recompensed.* 



Art. IV. — On Definitions ; by the Rev. D. Wilkie, of Quebec. 



No. I. 



As the adoption of correct logical definitions lies at the foundation 

 of many of the sciences, and is of the greatest utility in all of them, 

 and in every branch of knowledge, I hope no apology is necessary 

 for laying before the readers of this Scientific Journal a few remarks, 

 which observation has long suggested, or been suggesting to me. I 

 need not appeal to the great Locke for confirming the importance of 

 a subject, which, whether in the promotion, in the acquisition, or 

 the communication of knowledge, is equally manifest. Without a 

 constant reference to well defined terms, mistakes on the part of the 

 learner are innumerable ; errors in the teacher, or the writer, are 

 inevitable. 



In order to throw as much light as possible on this subject, let us 

 first observe its necessity, or the necessity of some substitute for it, 



* The scientific reader need not be reminded that these remarks do not bear 

 upon the radiation or absorption of heat accorapanjang light. 



