Mr. Livingpn on the Effeds of Shade, &c. 12 ~ 



thedired rays of light pafs through the tree, it mufl follow, 



that neither air nor water are folvents for this body j for if 



they were, it would be wafted in different directions. If this 



idea is juft, what a field does it open for important difcoveries? 



To how many medical purpqfcs may this new menflruum be 



applied? The only properties of vegetable fubftanccs with 



which we are acquainted, are thofe that we colled from the 



appHcation of the whole plant, or a folution of it in water or 



fome other liquid. By the firil of the means, we may indeed 



obtain thofe parts which light only can diffolve, but mixed with 



various fubftances which may probably count .^rad the effed. 



By the laft, this matter, whatever it may be, cannot be obtained. 



Many plants that are confidered as poifonous, when fubjeded 



to this trial, may be found to contain a falutary fubflance, and 



the rays of the fun paffing through them, be made to convey 



health and vigour. Should thefe conjedures be verified by 



experiment, the Phyficians may again claim Apollo for their 



patron, after having long abandoned him to the poets, to 



whom indeed they will feem, in fome fort to affimilate 



themfelves, when, inflead of pills and powdas, they fhall 



prefcribe zephyrs and funbeams. Will not this fad, in fome 



meafure, account for another, which feems well eilablifhed by 



Dr. Ingenhouz, to wit, that the effluvia of plants are falutary 



in the light, and hurtful at night ? The fads I have ftated 



are confirmed by a variety of intelligent farmers, to whom I 



Ff 



