§28 On the Powers of (he pr/fma/'ic Colours 



hcfs; and alfo permitted fomc heat to come to the eye by 

 tranfmitting chiefly red rays. 



No, 3. I apphed tv/o white ghides, with pitch between 

 them, to the telefcope; and fomid that it made the fun ap- 

 pear of a fcarlet colour. They tranfniitted fome heat j and 

 diftindlncfs was greatly injured. 



No. 4; I vjfed a vcrv dark green glafs to ftrtp heat; and 

 behind it, or towards the eye, I placed a red glafs to flop 

 light. The firfl glimpfe I had (if the fun was accompanied 

 with a fenfation of heat; diftinftncfs alfo was materially in- 

 jured. 



No. 5. I uftfd a dark green and a pale red; but the fun 

 not being fufFicichtly darkened, I fnioked the red glafs, and 

 putting a fmall partition between the two', placed the faioke 

 towards the srreeu glafs. This took off the exuberance of 

 liglxt ; but did not remedy the inconve nieilce ariling from 

 heat. 



No. 6. I ufed two pale green glafTcs, fmoking that next 

 to the eye, and placing it as in No. 5, fo that the fmoke 

 might be ir.clofcd between the two. This afted incompa- 

 rably well ; hut in a very fliort time, the heat which palled 

 the lird glafs (though not the fecond, for I felt no fenftitioil 

 of it in the eye,) difordor^d the fmoke, by drawing it up into 

 little: bliflcrs or liars, which let through light; and this com- 

 pofition therefore f :)on became ufcleft--. 



No. 7. I ufed two dark green glaffes, cine of them 

 fmoked, as in No. 5. Thefe alfo aftcd well ; but became ufe- 

 lefs for the reafon affigned in No. 6, though fomewbat lefs 

 fmoke had been required than in the former compofition. I 

 felt no heat. 



No. 8. I ufed one pale green, with a dark green fmoked 

 glafs upon it, as in No. 5. It bore an aperture of four 

 inches very w^ell, and the fmoke was not difordered J but 

 \vhen all the tube was open, the pale green glafs cracked in a. 

 few minutes. 



No. 9. Placing now a dark green before a fmoked green, I 

 favv the fun remarkably well. In this experiment I had made 

 a difference in the arrangement of the apparatus. The 

 Cracki-ng of the glaffes^ I fuppofed, might be owing to tbeit 



receiving 



