144 - On the Pneumatic Paradoz. 
= 
IT have taken proofs of microscopic objects magnified six hun- 
dred times, by receiving the image from a solar microscope on the 
iodized surface. Perfect pictures of the wings of insects and oth- 
er small objects were thus obtained. 
The attempts which have hitherto been made, to transfer the 
picture to paper, have been unsuccessful. In order that it may be 
less liable to injury, Dr. Berres, of Vienna, has published a meth- 
od of etching it “faintly” on the silver. In London, by using 
the graver, the plate with the picture on it, has been converted 
into an engraving plate. Of course, after such rude usage none 
of the peculiar beauty and delicacy of the Daguerreotype picture, 
appeared in the engraving. 
Medical College, New Haven, Dec, 17th, 1840. 
Arr. XVI.—Supplementary Note to the Article on the Pneumatic 
Parador in the last number of this Journal ; by JoserH Hane 
Axsot, Mem. Am. Acad. Arts and Sciences, &c. 
Since my article on this subject was forwarded to the editors, 
my attention has been drawn to a paper relating to the same phe- 
nomenon, by Mr. Thomas Hopkins, in the Memoirs of the Lite- 
rary and Philosophical Society of Manchester, published in the 
year 1831; of the circumstances connected with its discovery, he 
gives the following account, undoubtedly authentic, and differing 
in some important particulars from that which I copied from the 
London Mechanics’ Magazine :-— 
“On the 11th of October, in the year 1824, Mr. Roberts aflixed 
a valve to the aperture of a pipe, used as a waste-pipe, for the pur 
pose of regulating or equalizing the force of a blast of air, which 
was blowing a furnace. ‘To his surprise, however, he found that 
the valve, instead of being readily blown off by a strong current, 
remained at a small distance from the aperture of the pipe, 
was removed to a greater distance only by a considerable exertion 
of the power of the hand. 'This singular phenomenon was wit 
nessed by many gentlemen belonging to this society, in the same 
week, and appeared to be viewed by them all, as equally new 
and extraordinary.” 
I have to regret that, from the circumstance of finding errone 
ous explanations of the phenomenon in foreign scientific public 
