cxviii GENERAL SUMMARY OF SCIENTIFIC AND 



by such a process can the enormous waste and drain caused 

 by the fisheries as at i^resent prosecuted be met and replaced, 

 an expenditure of ten or fifteen thousand dollars per annum 

 being sufficient to secure the return in value of many hun- 

 dred thousand dollars in productive results. 



.The discovery of a species of grayling {Thymallus tricolor) 

 in certain rivers of Michigan, has suggested the importance 

 of making this fish more widely known, by introducing it 

 into appropriate w^aters elsewhere. Fish of this genus are 

 much esteemed in Europe, both as an article of food and as 

 furnishing excellent sport in their capture ; and the American 

 variety will probably be much sought after when arrange- 

 ments can be made to supply the spawn in sufficient quan- 

 tity. 



A very important advance in the artificial propagation of 

 fish was made by Seth Green and party wdiile in the service of 

 the United States Commission, in the discovery that striped 

 bass, or rock-fish {Eocciis linealus)^ may be bred as easily 

 and in much the same manner as the shad ; special effort 

 will probably be made during the coming year toward in- 

 creasing the supply of this most valuable fish. 



MECHANICS AND ENGINEERING. 



A review of the condition o^ tho, Iron producing and man- 

 ufacturing industries for the year (1873) presents a picture 

 of great prostration. From the statistics of the American 

 Iron and Steel Association, it appears that fully 07ie half of 

 the furnaces have been blown out ; w^hile the rollinsf-mills 

 are either w^orking on short time or are bare of orders, and 

 the mining of iron ore has slackened to a corresponding de- 

 gree. 



This condition of things, so very different" from the unex- 

 ampled prosperity of the preceding year, is to be attributed 

 to the great restriction of the building operations of railroads 

 and especially of Western roads and the present almost 

 absolute suspension of farther railway extension as one of 

 the immediate results of the present financial crisis. 



During the year 1872 forty new furnaces were erected in 

 various parts of the United States, and the erection of others 

 was undertaken; and the extension of rolling-mills, etc., kept 

 pace with the increased producing capacity wliich they rep- 



