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POPULAR SCIENCE MONTHLY 



telescopes were first invented all the astronomers have been look- 

 ing at Mars, and yet they never noticed (their telescopes were not 

 good enough) those interesting satellites which the acute observa- 

 tion of Professor Hall detected with the help of the great telescope 

 of the Naval Observatory at Washington. This discovery was fol- 

 lowed by another of a still more delicate nature, when that con- 

 summate observer, Professor Barnard, using the great Lick tele- 

 scope, detected the fifth satellite of Jupiter. This is indeed a most 

 difficult object to observe, requiring, as it does, the highest optical 

 power, the most perfect atmospheric conditions, and the most skill- 

 ful of astronomical observers. "We may take this observation to 

 represent the high-water mark of telescopic astronomy in the nine- 

 teenth century. This being so, it may fitly conclude this brief 

 account of some of the most remarkable astronomical discoveries 

 which that century has produced. 



THE APPLICATIONS OF EXPLOSIVES. 



By ClIARLKS E. MUNKOE, 



PEOFESSOE OF ClIEMISTEY, COLUMBIAN DNIVEESITY. 



THERE is something about fire which fascinates every one, yet 

 the action of explosives arouses even a livelier interest, since 

 the accompanying fiery phenomena are more intense and are at- 

 tended with a shocking report and a violent destruction of the sur- 

 rounding material, while this train of events, with all its marked 



Gun-Cotton Factory. I)i|>iiiiifr cottini in nitratiiif,' troughs. 



