on the Porosity of Bodies, u .^n 293 



been able to mistrust the aplanatic eye-piece of my microscope. 

 A real doubt as to the objective nature of those spaces, more- 

 over, after long and repeated occupation with the same object, 

 could not last longer, as with alternate elevation and lowering 

 of the minute objects, and with alternately increased and dimi- 

 nished illumination, I distinctly saw the light flash through 

 them ; and even in examining the larger dust-particles, could 

 follow the spaces in all gradations j from complete opacity through 

 the different degrees of the diaphanous to entire transparency. 

 Although, therefore, I was at first much inclined to take what I 

 saw for an optical illusion, long examination compelled me, 

 entirely to abandon such a thought, — ever convincing me anew 

 that porosity is a constant formation common to all dust-particles 

 without exception, and that the pores in the larger of them are 

 either wholly or in part covered, through the lying one upon 

 another of several lamellae and scales. 



This discovery prompted me to examine other organic and 

 inorganic bodies also in a like manner, i. e. without the addition 

 of watery and in as minutely divided a condition as possible. I 

 took, for example, a morsel of dried bladder of the hog, and 

 holding the same over a clean glass, freed from all dust, scraped 

 most gently on it with a sharp knife, so that extremely small 

 portions, scarcely visible with the naked eye, fell therefrom upon 

 the glass ; covered these with glass, likewise cleansed from all 

 dust, in order to avoid any confounding with other particles, 

 and then under the microscope sought out the smallest of the 

 said scrapings. The porosity of these appeared with a distinct- 

 ness just the same as in the minutest dust-particles, in casses 

 where the scrapings had been made with sufficient minuteness, 

 and where of these again only the minutest were selected for 

 examination. 



In the larger scrapings also, where their too great thickness 

 did not render them opake, I was at any time able with certainty 

 to recognize the higher or lower degree of the diaphanous, as 

 well as a loose, richly spaced structure, in their whole extent ; 

 consequently distinct traces of porosity. 



Since then 1 have with perfect certainty recognized, as well 

 individual microscopic pores, as also generally a highly porous 

 structure, not only in all the organic, but also in all inorganic 

 bodies, access to which was possible, even granite and the metals, 

 and, as will be more amply stated further on, have with the mi- 

 crometer measured the pores. 



The methods therein followed I now put together in a few 

 words. 



[To be continued.] 



