Miscellanies. 389 



\ 



The following observation of Dr. H. is, perhaps, sufficient to es- 

 tablish the supposition above made. 



" On the subject of Alexipharmics, I may observe, that those plants 

 which are regarded as antidotes or counterpoisons, are chiefly those 

 eminently bitter, aromatic, and piquant, — being the most powerful 

 warm sudorifics." 



" We know that the Corymbiferae afford many examples of this 

 sort ; but the Guaco, although of this naturaj order, is almost entirely 

 destitute of the forenamed sensible properties ! !" If any one could 

 take into his mouth a portion, however small, of the Mexican Guaco 

 sent hither, and especially could swallow a teacupful of the infusion, 

 he would be impelled to give a different account of its sensible prop- 

 erties. Dr. H., moreover, cites some cases in which the Guaco, or 

 what he understood to be such, was tried ineffectually in the case of 

 rattlesnake bite. This may be very possible, without derogating in the 

 least degree from the credibility of Mutis, Chabert, his Mexican au- 

 thorities and correspondents, or the statements from Venezuela, al- 

 ready presented in this number. W. R. J. 



4. Optics. — A treatise on optics, by Sir David Brewster, has been 

 published by Carey &; Lea. It is from the "hand of a master," and 

 has been adapted to the use of colleges in this country, by an appen- 

 dix from Professor Bache, of Philadelphia. 



4 The work presents the results of experiment and theory, applied 

 to the investigation of different branches of optical science. 



The phenomena of double refraction, and the polarization of light 

 are treated of, and explained much at length; The author suggests 

 new views on some points which had received the sanction of Sir 

 fsaac Newton, particularly his theory of the colors of natural bodies, 

 one of the most interesting branches of natural science. It is Sir 

 D. Brewster's opinion, that although Sir Isaac incontrovertibly proved 

 " that the colors of material nature are not inherent in colored bodies;" 

 that yet, the rules by which he supposes the combinations of light 

 produce transparency, opacity, and the varied tints which embellish 

 the different forms of matter are insufficient and unfounded. He 

 deems the " Newtonian theory of colors, applicable only to a small 

 class of phenomena, such as the colors of the wings of insects, the 

 plumage of birds, the oxidized films on metal and glass, and certain 

 opalescencies ; while it leaves unexplained, the colors of fluids and 

 transparent solids, and all the beautiful hues of the vegetable king- 



Vol. XXIV.— No. 2. 50 



