cxxii GENERAL SUMMARY OF SCIENTIFIC AND 



The production of Coal in the United States for the year 

 just passed will, in consequence of the serious prostration of 

 the iron producing and manufacturing industries, fall some- 

 what below the figures of 1872, as a natural consequence. 



In this connection, the most instructive feature of the sub- 

 ject for our yearly summary of progress is to be found in 

 the very general attention to the utility and expediency of 

 introducing into American mines the system of raining coal 

 with the aid of coal-cutting machines, which have proved 

 themselves so economical and such practical solvers of labor 

 difficulties abroad. The subject has been the theme of dis- 

 cussion before several of the American enojineerino- societies 

 during the year, and the system generally pronounced to be 

 susceptible of much less utility here than abroad ; inasmuch 

 as the economy of such machinery, according to the best-in- 

 formed judges, will be in the inverse ratio to the thickness 

 of the veins on which it is employed. In most American 

 localities where the mining of coal is largely carried on, the 

 veins are of considerable, often, indeed, of enormous thickness, 

 as compared with those of European countries ; the waste is 

 therefore less, the production far greater with equal labor, 

 and consequently the necessity for machine-work less urgent 

 than there. In the Indiana coal-mining district, however, 

 where the coal seams are comparatively thin, coal-cutting 

 machinery of American design was introduced during the 

 last year, and from the statements of the mine owners, has 

 proved itself to be very advantageous on the score of econ- 

 omy. It is probable, therefore, that the success of this first 

 experiment will inaugurate the general introduction of such 

 machinery in this country where the conditions are similar; 

 so that our next year's summary may find this innovation to 

 be a very general practice. This inference is warranted by the 

 statement that in England, where these machines have been 

 very largely introduced during the past year, and where the 

 coal seams have an average thickness of from two to three 

 feet, it is estimated that 60,000 men only would be required, 

 with their aid, to raise the 120,000,000 tons annually put out, 

 instead of the 360,000 now called for. 



In connection with the same subject, the question of the 

 utilization of the coal-waste, or slack, can not be passed by 

 without a brief notice of the attempts which have been made 



