OF LA PF.R0US1. 19 



Minor. It was with frefh furprife that I per- 

 ceived all the contours of my body traced in the 

 beautiful colours of the rainbow, on fome 

 clouds that were below me, on the tide oppofite 

 to the fun. 



The folar rays, which are divTbived in pairing 

 on the furface of bodies, give a veryjuft expla- 

 nation of this brilliant phenomenon. It repre- 

 fents, on a large fcale, the experiment known to 

 natural philofophers, by which the rays that are 

 juft made to pafs on the furface of an opaque 

 body, fituated at the opening of a window, re- 

 prefent all the contours of that body in the co- 

 lours of the rainbow, after having been concen- 

 trated in the middle of a lens, in order to be 

 afterwards received on a piece of white paper. 



We had juft paffed over prodigious heaps of 

 pumice-ftones, among which we remarked few 

 vegetables/ and thefe were very weak. Some 

 brooms were the only fhrubs that profpered at 

 fuch an elevation. 



We walked with conflderable difficulty over 

 thefe volcanic fragments, for we funk into them 

 half way up the leg. 



Some blocks of pozzolana were here fpread at 

 a pretty great diftance from each other. 



It was nine o'clock in the evening, when we 



took up our quarters -for the night in the midfl 



of the lava, fome large fragments of which were 



c a the 



