on the Porosity of Bodies, ::'"'■ . '! 871 



diameters linear and full transmitted light. The microscope 

 stood 4 to 6 feet from the window. The covering-glass 

 was employed in order to prevent any confounding with other 

 particles that might possibly fall upon the glass during the 

 examination. Of the scales and lamellse in the field of view I 

 then sought out the smallest. Those scales which, from their 

 minuteness, are scarcely or not at all visible with the naked eye, 

 are best adapted for perception of the pores. There is seen a 

 delicate net and lattice-work of variously interlaced fibres, with 

 lamellae more or less covering one another, which, however, 

 partly between them, partly in their substance itself, present a 

 multitude of minute, irregularly shaped, roundish, elongated, 

 indented, and angular orifices, spaces, or rifts, which are some- 

 times dendritically branched, and form a system of communi- 

 cating hollows, interstices, or passages. 



b. The making of minute scrapings of dried animal membranes 

 and other animal formations, for example, bones, enamel of 

 the teeth, egg-shell, horn, &c., as well as of soft metals, such as 

 gold, silver, lead, is not difficult ; but with very hard bodies, 

 such as granite, iron, and many crystals, it is not to be accom- 

 plished, because by their hardness the knife is too much laid 

 hold of, and the detritus hence arising might easily be confounded 

 with the scrapings of the formations intended to be examined. 

 In examining the harder bodies, therefore, I have thought it 

 fitting to use two substances of the same kind, for example, two 

 pieces of steel, granite, &c., which, held over a glass from which 

 the dust had been wiped ofi^, were gently rubbed the one upon 

 the other. The detritus, either falling from or cleaving to the 

 substance, was then covered with glass for examination. 



In both ways I succeeded with certainty in recognizing in all 

 solid bodies, not merely at their surface, but through the whole 

 thickness of their substance, and in all their parts, sometimes 

 marks of general porosity, sometimes even individual pores; 

 and very interesting was it to notice a surprising concordance 

 between the disposition of their parts and that of their minuter 

 structure. Thus if the attention be directed to the smallest 

 particles of the detritus so obtained, the addition of water being 

 avoided, there mry be perceived in all bodies the minute dis- 

 position and arrangement of delicate granules, filaments, scales, 

 and lamellae; producing the conviction that the expression struc- 

 tureless, now -a- days so great a favourite in histology, can have a 

 title to be used only in so far as it is intended to denote the 

 condition hitherto of our knowledge, namely, the absence of 

 (what is already known and has been erected in the system 

 under fixed names) the morphological elements of texture. 

 The smallest atom is not really structureless I The microscopic 



