Of Light and Colours.

the Square of the focal Distance inversesThus suppose the Surface or Area °*one Glass contained 12 square Inches,its focal Distance were 8 Inches; and th®Area of another Glass were 9 square Inchedand its focal Distance 4 Inches ; then th®Effects or Intensity of Burning would be aS44 to 4-61 or as 12 X 16 to 6 X 64, viz.

19710576 (CXIV).

11. The Effect of Fire in burning consists in th>^that the Velocity of the Particles of Fire so far incrca*ythe Velocity of the Parts of the Body to which >*■applied, as to cause a separation beyond the Spherescorpuscular Attraction, by which means the Body

be dissolved, and the Particles which are vosotile v ' r Jfly oss in the Form of Steam, Smoak, Fume, ™ £while that which remains appears in the FormCoal, Calx , AJhes, Caput Mortuum , &c. .

12 . The Parts of some Bodies are extremely v °; „

tile, and will most of them be dissipated by the A<m sof Fire ; but others again are to be found whose Qare of such a Nature, or so fixed, as not to y>d°the Force of Fire, or the Velocity communicatedthem will not be able to dissolve the corpuscular AtQtion ; but when this glowing Velocity of the P^P'pbated, car, in other Words, when the Fire in TBody is extinct, the Parts (and of course the wh°Body) appear unalter’d. Of which Sort of Substjd)we have a noble Instance in that Fossil call’d the Stos or Amianthus Stone. This Stone is found inParts of the World ; particularly in Wales a greatmay be seen adhering to, and growing up withStone of many of their Quarries. 0 (

(CXIV) 1. In order to account for the N ature vl ,eBurning-tGi-asses, whether Mkrours or ^