44 REPORT OF THE SECRETARY. 



series of investigations, was made iu regard to petroleum, but at that 

 period the ouly refined petroleum submitted to the board after advertise- 

 ment was that of a volatile character, and too dangerous to be adopted 

 for light-house purposes. Since then, however, the price of lard-oil 

 has constantly increased, while refined petroleum can now be obtained 

 of such a character as to be safely employed by ordinary light-house 

 keepers. Its introduction, therefore, in regard to economy, is a matter of 

 much importance. But great care must be exercised iu selecting oil of 

 a proper quality, and hence the necessity of a thorough knowledge of its 

 l^eculiarities in regard to safety. 



In the investigations on this subject, it was ascertained that the fire- 

 test usually employed to establish the character of a given oil in reference 

 to safety was not in itself sufficient to settle this question. Many of 

 the oils in general use, which, at the temperature of the atmosphere, in- 

 creased by that from the burning of the lamp, give off a vapor which, if 

 suffered to accumulate and mingle with the air in the space above the 

 oil in the reservoir, produces a mixture which, if in definite proportion, 

 explodes with the violence of gunpowder. It is true, on the doctrine of 

 chances, an explosion may seldom take place, but still, the conditions 

 necessary are frequently present, and only requires the application of a 

 flame to produce a disastrous effect. 



Although the discovery of the petroleum wells of Pennsylvania has 

 been an immense boon to humanity, yet the advantage gained from it 

 Las been dearly bought by the accidents which have resulted from its 

 incautious use. Its sale ought to be regulated by rigid enactments of 

 legislatures, and none suffered to be sold which exhales a vapor capable 

 of producing an explosion when mixed except at a temperature much 

 above that at which the lamp is subjected in the warmest period of the 

 year. 



Fish Commission. — The investigation in regard to food-fishes and the 

 methods of their propagation, for which an appropriation for several 

 years has been annually made by Congress, has been continued under 

 the direction of Professor Baird. This work was commenced iu 1872, 

 and has been jirosecuted with satisfactory results to the present time. 

 The species to which special attention has been given are shad, the 

 fresh-water herring, the striped bass or rock-fish, the California salmon, 

 the salmon of Maine, the land-locked salmon, the white-fish, and the 

 carp, each of these having special relations to certain portions of the 

 country, and promising in their anticipated aggregate an extremely 

 important addition to the food-resources of the United States. 



The States which have, up to this time, been the recipients of spawn 

 and young fish are thirty-two in number. The extension of the benefit 

 to other States, and its amplification in all, is simply a question of time 

 and expenditure. The subject of fish culture is one of general popu- 

 larity, as is evinced by the appointment of fish-commissioners iu nine- 

 teen States, in most instances for the purpose of direct co-operation 

 with the United States Commission. 



