CAUTIONS NECESSARY. 



177 



the confidence of the mariners, and vastly increase the 

 perils of navigation. 



The public authorities are, therefore, very cautious about 

 introducing new modes of producing light, especially such 

 as depend upon any chemical process. Of course the oxy- 

 hydrogen light requires the preparation of both oxygen 

 and hydrogen, and the electric light that of a current of 

 electricity. The former renders necessary a chemical pro- 

 cess involving the maintertance of a somewhat complicated 

 apparatus, and a certain degree of scientific supervision in 

 the management of it. These constitute insuperable ob- 

 jections to it in respect to a vast majority of the situations 

 in which lights are required. 



These situations are sometimes quite isolated, light- 

 houses being not unfrequently built on rocks at some di 



