Baths of Nero, Bay ofBaja, near Naples. 247 



and difficulty in breathing is greatest, for we afterwards turn 

 pretty sharply to the right, and, descending gently, breathe a 

 more tolerable atmosphere, though nearer the source of heat. 

 After going about sixty paces farther, I reached the hot 

 spring, and, by keeping my head near the ground, I found 

 that I could have remained a considerable time without much 

 inconvenience. The pool of water there formed seemed to 

 have accumulated in a passage originally cut to a greater 

 length, since the water rose to the roof from its slanting di- 

 rection. From the confusion of the moment, and the apparent 

 unnaturalness of a spring hotter than the hand can bear, I 

 put my finger into it, but rapidly withdrew it, with a sensation 

 nothing short of the heat of boiling water. I held in my hand 

 a mercurial thermometer of Cary's, which I dipped into the 

 spring, and reading off the indication by the light of a torch 

 carried by our guide, with as much deliberation as possible, 

 I found it to be 183°. 5. I had reason to believe, however, 

 from previous observation, that at this part of the scale it 

 would require a reduction of 1°; I therefore placed the tem- 

 perature at 182°. 5. It was on the 11th December, 1826. 

 This observation is the more valuable, that, as far as I know, 

 it is the only one affecting accuracy yet given to the world. 

 Most authors have asserted that the water boils ; and Roma- 

 nelli distinctly asserts that its temperature exceeds 80° Reau- 

 mur, though it is obvious enough he could never have tried it. 

 Breislak, with great moderation says, "La chaleur qui y regne 

 a une grande intensite; Pobscurite du lieu, et la vapeur qui 

 s'attache a la surface de tous les corps, empecheut de lamesu- 

 rer avec precision, mais elle passe les 60 degres de Reaumur." 

 But 60° R. =z 167° Fahr. so that Breislak comes below the 

 mark. 



It is not surprising that the idea of so great a heat as this 

 should have been alarming to those unacquainted with the 

 powers of animal life to withstand intense heat, when we re- 

 flect that the time is not very long past when the experiments 

 of Blagden and Fordyce put this question in its true light. 

 The most intense heat, however, sustained by these gentle- 

 men seems to have been in dry air, which has far less effect 

 on the body than an atmosphere loaded with steam, which, 

 by condensing on the body, parts with a large share of its ca- 

 loric. These experimenters, however, found far less incon- 

 venience than they expected from the great temperature. 

 Their bodies when exposed to steam of a moderate tempera- 

 ture became inflamed,, the pulse much quickened, but the heat 

 of the body little affected. In passing to the cold air they 

 felt little inconvenience, probably from the excess of moisture 

 and perspiration which defended the pores of the skin from the 



