VOL. XC.] PHILOSOPHICAL TRANSACTIONS. 631 



mediately from the sun, are many and important ; but the observations on that 

 species of light which is spontaneously emitted from various bodies, are not only few 

 in number, but in general very imperfect. The author is therefore desirous of 

 drawing the future attention of the philosopher more particularly to this subject, 

 and of communicating his own experiments and observations on it, to the r. s. By 

 the spontaneous emission of this light, the author wishes to distinguish it from atf 

 kinds of artificial phosphorus ; which, as he apprehends, differ essentially, in some 

 of their properties, from that light of which he means to treat. And, by its ad- 

 hesion to bodies with some degree of permanency, he distinguishes it from that 

 transient sort of light which is observable in electricity, in meteors, and in other 

 lucid emanations. The light which is the subject of this paper, he therefore dis- 

 criminates by the name of spontaneous light. 



The substances from which such light is emitted, are principally the following. 

 Marine animals, both in a living state, and when deprived of life. As instances of 

 the first may be mentioned, the shell-fish called pholas, the medusa phosphorea, and 

 various other mollusca. When deprived of life, marine fishes in general seem to 

 abound with this kind of light. The hon. Mr. Boyle commonly obtained light, for 

 his use, from the whiting, as appears from many parts of his works : Dr. H. pro- 

 cured his fish light chiefly from the herring and the mackerel. The flesh of qua- 

 drupeds has also been observed to emit light. Instances of this are mentioned by 

 Fabricius ab Aquapendente ; by T. Bartholin ; by Mr. Boyle ; and by Dr. Beale ; 

 for which, see T. Bartholin, de luce animalium, p. 183; Boyle's works, vol. 3, 

 p. 304 ; Phil. Trans, vol. 1 1, p. 5QQ. In the class of insects are many which emit 

 light very copiously, particularly several species of fulgora or lantern-fly, and of 

 lampyris or glow-worm; also the scolopendra electrica; and a species of crab, called 

 cancer fulgens. Rotten wood is well known to emit light spontaneously. Peat 

 earth also has the same property. Of the effects of the latter, a remarkable instance 

 is related in Plot's Nat. Hist, of Staffordshire, p. 115. 



The place where the following experiments were made, was a dark wine-vault, 

 which, for distinction's sake, the author calls the laboratory. The heat of this la- 

 boratory varied, throughout the year, from about 40 degrees of temperature to 64°. 

 The thermometer made use of was that of Fahrenheit. The weight is always to be 

 supposed that called Troy weight. The liquid measure employed, was that used 

 for wine in this country : the ounce containing 8 dr. avoirdupois ; and the pint, 



house, London, in 1807. It would seem that he studied physic at Edinburgh, as we find published there 

 an inaugural dissertation, " DeScorbuto," 176*5, afterwards reprinted in 1768, both in Latin and English. 

 He published also a treatise on the Puerperal Fever, Lond. 1772. Dr. H. practised medicine during a 

 long course of years in London, with considerable reputation, and was elected physician to the Charter- 

 house, in 1774, which appointment he held to the time of his death. He lost his life in consequence of 

 the chimney of his house being blown down ; when, getting up through the trap-door to the roof, to see 

 what damage had been done, he fell from the steps, so as to cause a violent concussion of the brain> 

 which in a few days terminated fatally. 



