clxxxiv GENERAL SUMMARY OF SCIENTIFIC AND 







neously. The apparatus used for producing the current was 

 the Gramme machine. It may also be remarked in this 

 branch of our Summary that the use of natural gas for fuel 

 in various quarters has been considerably extended, the last 

 year having witnessed its introduction for industrial uses in 

 a number of places. 



While no novel or revolutionizing inventions have ap- 

 peared during the past year in the field of illumination, our 

 technical record would be incomplete without mentioning the 

 substantial progress achieved by the advocates of the water 

 gas and petroleum gas. The late meeting of the "American 

 Gas-light Association" a body representing a large share of 

 the talent employed in this country in gas manufacture was 

 occupied almost exclusively with the discussion of the proc- 

 esses just named. The chief interest, however, was centred 

 upon the performance of the most recent of these innova- 

 tions the so-called Gwynne -Harris process. Briefly de- 

 scribed, the essential features of these patents is the employ- 

 ment of clay retorts (instead of iron) in which the decompo- 

 sition of superheated steam is effected. The superheating is 

 done by the employment of superheaters of clay set in the 

 hottest portions of the bench the object of which disposi- 

 tion is to secure the perfect conversion of every particle of 

 watery vapor into superheated steam before it enters the 

 decomposing retort. The decomposition is effected by pass- 

 ing the superheated steam into a heated retort supplied with 

 anthracite coal ; the introduction taking place through a 

 cellular bottom formed of perforated tiles. The steam is 

 thus made to flow in a regulated manner from below up- 

 ward, by numerous small openings, through the highly heat- 

 ed anthracite; and the decomposition of the same into hy- 

 drogen and carbonic oxide, effected with such regularity as 

 to afford practically uniform results. The mixed gases re- 

 sulting from this decomposition are then passed through re- 

 torts charged as usual with bituminous coal, so as to secure 

 the uniform admixture of the water-gas with the products 

 of the bituminous-coal distillation, and producing an illumi- 

 nating gas of uniform composition and permanent character. 

 The difficulty of perfectly decomposing the water into the 

 two gases above named, which appears to have been an in- 

 superable obstacle to the success of previous inventions of 



