viii PREFACE. 



many colors, present a series of wonders which must excite the 

 admiration of the most indifferent observer. 



In the United States, there are ten thousand enrolled young nat- 

 uralists, comprising the Agassiz Association. As one of a com- 

 mittee solicited to answer questions propounded by the young 

 people, members of this association and of the Chautauqua Circle, 

 I have often been surprised at the nature of the queries, which 

 shows that this army of young observers includes many who are 

 not merely collectors of curiosities, but are naturalists in the best 

 sense. They are systematic inquirers, and working in the right 

 direction to become scientists, should they continue. 



It is to these young scientists, their unscientific elders, and the 

 boys and girls in general who have not yet had their interest aroused 

 in Nature's works, that this volume is addressed ; and if some infor 

 mation is conveyed, while appearing merely to entertain, one object 

 of the author will have been accomplished. 



The subject of phosphorescence is one which affords the widest 

 field for investigators ; as, while the most careful descriptions of 

 the light-emitting organs have been made, the actual cause of ani- 

 mal phosphorescence is unknown. Material for study is ever at 

 hand ; the fire-fly courts attention at every summer door-yard, and 

 the pools of beach and cove are illumined by ocean forms. Even 

 the simplest experiments are of the greatest interest. I have read 

 by the light of a luminous beetle, and have determined the time of 

 night while holding my watch in the glare of ocean animals. Von 

 Bibra wrote his description of the Pyrosoma by its own light ; the 

 shark of Bennett illuminated his cabin like a chandelier ; photo- 

 graphs have been taken by the light of luminous beetles and 

 by phosphorescent plates ; and probably the day is not distant 

 when more important uses will be found for this wonderful light, 

 which, in default of a better name, we term phosphorescence. It 

 is found in the animal, vegetable, and the mineral kingdoms ; m 

 life and in death; in growth and in decay. It illumines, but 



