THE BOOK OF THE LANTERN. 73 



also tried ; but besides wasting away rapidly, it proved 

 inferior even to magnesia. 



" Of these substances, and also of their compounds with 

 one another, lime appearing to possess a decided superiority, 

 my subsequent experiments were confined to it alone, and 

 by a more perfect adjustment of the apparatus, by bringing 

 the maximum heat, which is confined within narrow 

 limits, exactly to the surface of the lime ball, and by using 

 smaller balls than those employed in the early experiments, 

 a very material increase of light has been obtained. The 

 mean of ten experiments, made lately with every pre- 

 caution, gives for the light emitted by lime, when exposed 

 to this intense heat, 83 times the intensity of the brightest 

 part of the flame of an Argand burner of the best construc- 

 tion, and supplied with the finest oil. The lime from chalk, 

 and such as is known at the London wharfs by the name of 

 flame lime, appears to b3 more brilliant than any that has 

 been tried. When well-burned Carrara marble is made 

 into a paste with water, and gradually dried, it appears to 

 be nearly equal to the preceding ; when strongly com- 

 pressed, or very porous, it is inferior." 



The best limes to be obtained are of the kind known as 

 "hard," or "Nottingham limes." These last better than 

 any others that I know of. They are sold in tin boxes 

 holding one dozen each, and are packed in powdered lime, 

 kept as far as possible from the air. Let it be remembered 

 that these limes will be spoiled by exposure to damp air. 

 By such exposure they swell to double their normal size, 

 will break the strongest box in which they are confined, 

 and will, finally, fall to powder. In other words, they are 



