104 EMISSION OF LIGHT J5F 



death, none perhaps so vividly as that of the Pholas, 

 a mollusk well known to those who reside on the 

 coast. That this mollusk was luminous after death 

 was known to Pliny, who said that it shone in the 

 mouths of the persons who ate it ; and among 

 the moderns, Keaumur, Beccaria, Marsilius, Galea- 

 tus, and Montius have studied its phosphores- 

 cence. 



Beccaria had the curiosity to ascertain how 

 the light of putrescent fish, and that of the dead 

 pholas, affected different colours, and for this pur- 

 pose he placed in the light emitted, pieces of dif- 

 ferent coloured ribbons. The white came out 

 brightest, next -to that was the yellow, and then 

 the green-, the other colours could hardly be per- 

 ceived. The same experiment was repeated, with 

 similar results, on trying coloured liquids in glass 

 tubes. We have here then another instance of the 

 predominance of yellow tints over the others in 

 cases of phosphorescence. Indeed Sir Isaac New- 

 ton, who first decomposed light into the seven 

 rays of the spectrum, says, " The most luminous 

 of the prismatic colours are the yellow and the 

 orange ; these affect the senses more strongly than 

 all the rest together." 



These experiments of Beccaria were made chiefly 

 with the Pholas. A single pholas rendered seven 

 ounces of milk so luminous that the faces of per- 

 sons might be distinguished by it, and it looked 

 as if transparent. 



