70 FSDESJlIi BBPOBTEB, �or soda. It îs, therefore, chemically distinct from quartz, and ÎB classed by mineralogists with the opal, as a minerai species distinct from quartz. In support of which I would refer to Dana's Text-book of Mineralogy, published by John Wiley & Sons, 1877, pages 262 to 267, inclusive, on which last page, under the species opal, reference is made to infusorial earth, and where the statements which I have made as to its density and hardness are corroborated. �"In respect to their properties as applied to the fiUing of wood, I would call attention to the fact that the two boxes, Exhibits L and M, contain the same weight of their respective contents. The mass of quartz, weighing four pounds eleven ounces, is about seven inches long, three inches wide, and four inches high. The infusorial earth occupies a box ten inches long, seven inches wide, and five inches high, being in the form of lumps of various sizes, but are evidently several times more bulky than the same weight of quartz, and sev- eral times more bulky than the quartz would be if it were reduced to powder such as is specified as employed in the Wheeler patent. This great difference is due to the porosity of the infusorial earth. Not only are the lumps of infusorial earth made up of loosely-cohering infusorial shields or frag- ments of shields, but these shields themselves have a very delicate structure, as seen under the microscope, so that the infusorial earth, from its spongy texture, is capable of absorb- ing and holding in its pores a considerable bulk of liquid. �"This difference of mechanical texture corresponds to a dif- ference in the adaptation of these two materials to use as a wood filler. The infusorial earth is porous in a degree com- parable to the wood which it is claimed to fill, so as to dimin- ish the absorption of oil or varnish, and must therefore act very inef&ciently as a filler. �"Again, the quartz, powdered, as specified in the Wheeler patent, is seen under the microscope to consist of sharp, angular particles, which, when applied to the surface of wood, by rubbing with a cloth or leather pad, are foroed into the pores of the wood, where they firmly lodge, and effectually fill these pores with an impervious material. The hardness of quartz ����
