•250 BLUE GLASS PHOTOGRAPHY. 



Thomas Blanchard, for turning irregular forms), the total had reached 

 10,041 ; or, for the period of sixty years comprised in the first era, the ag- 

 gregate amounted to 17,447. Yet in this small number are included Whit- 

 ney's cotton gin, McKean's first steam saw mill, Whittemore's wool and 

 •cotton card-making machine. Hare's oxy-hydrogen blowpipe, Blanchard's 

 tack machine, Fulton's steamboats. Hall's breech-loading fire-arms, Perkin's 

 stcfel engraving, Steven's tubular boiier and screw propeller, Lowell's power 

 loom, Burden's horseshoe and spike machinery, Mott's stoves for small coal, 

 Saxton's magneto-electric machine, Bogardus' ring flyer for cotton spin- 

 ning and the long category of other important devices of that wonderfully 

 prolific inventor. Professor Henry's splendid electro-magnetic discoveries, 

 Morse's telegraj)h, Guthrie's discovery of chloroform, Boyden's patent 

 leather, Baldwin's improvements in the locomotive, Howe's pin machine, 

 McCormick's rea]3er, Colt's revolvers. Wells' hat body machine, Goodyear's 

 vulcanization of India rubber, Bigelow's carpet loom, Howe's sewing ma- 

 chine, Sickel's cut-off, Morton's discovery of the anassthetic qualities of 

 •chloroform. Hodman's hollow casting of ordnance. House's printing tele- 

 graph, and Ericsson's steam fire engine. . 



To show with what rapidity inventors made improvements on inven- 

 tions embodying original principles, it may be noted that in the early days 

 of the sewing machine one hundred and sixteen patents were granted for 

 improvements thereon in a single year; and out of the 2,910 patents issued 

 in the year 1857, one hundred and fifty-two were for improved cotton gins 

 and presses, one hundred and sixty-four for improvements in the steam en- 

 gine, and one hundred and ninety-eight for novel devices relating to rail- 

 roads and improvements in the rolling stock. In the year 1848, three years 

 after the publication of this paper was commenced, but six hundred and 

 sixty patents were granted; but under the stimulus of publishing those in- 

 ventions as they were patented, ten years later, in 1858, the number had 

 increased six-fold, reaching 3,710, while up to January 1st, 1850, as already 

 stated, the aggregate of patents issued amounted to 17,447; since that time 

 and u]0 to the present the total is 181,015. 



Curiosity here leads us to review our own work, extending back for, 

 say, twent}^ years, or to 1857, a period during which 170,745 patents have 

 been issued. We find, by actual count, that 62,662 applications have been 

 made through the Scientific American Patent Agency for patents in the 

 'United States and abroad. This averages almost ten applications per daj^, 

 Sundays excluded, over the entire period, and bears the relation of more 

 than one quarter to the total number of patents issued in this country up 

 to the time of writing. — Scientific America?!. 



BLUE GLASS PHOTOGRAPHY. 



The blue-violet glass mania abroad seems to be confined to the photo- 

 graphers, and the conflict over the deceptive theory is being waged, not on 



