24 MEMOIE OF BUFFON. 



etruction of the lenses. These accomplished, he com- 

 menced' to build his great mirror. It was composed 

 of 168 pieces.of plain silvered glass, six inches by eight 

 in size, and he requited to examine above 500 pieces 

 before the most perfect could be obtained. Between 

 each was an interval of four lines, to allow a free 

 motion, and to permit the observer to see the place, 

 to which the images were to be thrown. The 

 whole were mounted in an iron frame, so fitted 

 with screws and springs, that a motion could be 

 given to them in any direction, and the images 

 reflected from all the mirrors easily thrown upon 

 the same spot. In eight experiments, he obtain- 

 ed the following results, which clearly show the 

 possibility of setting fire to the Roman fleet : On 

 March 23d, a plank of tarred beech was set on fire at 

 sixty-six feet, with only forty mirrors, and without 

 the mirror being put upon its stand. On the same 

 day, a plank tarred and sulphured, and having the 

 mirror more disadvantageously placed, was fired, at 

 the distance of 126 feet, with 98 mirrors. On the 3d 

 of April, at four o'clock in the evening, a slight in- 

 flammation was made upon a plank covered with wool 

 cut into small pieces, distant 138 feet, with 112 mirrors. 

 The next day, at eleven o'clock forenoon, 154 mirrors, 

 at the distance of 150 feet, made a tarred plank smoke 

 to such a degree in two minutes, that it would have 

 been inflamed had not the sun disappeared. On the 

 5th April, a dull day, at three o'clock afternoon, 154 



