144 On the Pneumatic Paradox. 



I 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 ma}?" 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. 17tli, 1840. 



Art. XVI. — Supplementary Note to the Article on the Pneumatic 

 Paradox in the last niimher of this Journal ; by Joseph Hale 

 Abbot, 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 1 Ith of October, in the year 1824, Mr. Roberts affixed 

 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, and 

 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 publica- 



