Page:Federal Reporter, 1st Series, Volume 5.djvu/81

 BBIDGBPORT-WOOD FINISHINO 00. ». HOOPBB. 69 �facts. The defendant'» expert was not called upon in regard to the differences between the properties of the two articles with reference to their practical use. Prof. Johnson t«s- tified : �"By the term 'silicious mari' I should understand a fine, aandy, or earthy material, consisting of clay, silica, in the two forma of sand, and so-called infusorial shields, which are the skeletons of microscopic plants. The infusorial earth oon- eists more largely or chiefly of these infusorial shields. Both the terms 'silicious mari' and 'infusorial earth' are consider- ably indefinite, and a large variety of different materials may be classed under these names. In the statô of New Jersey there occur various deposits, bearing the names 'green sand mari,' 'chocolate mari,' 'gray mari,' 'ash mari,' 'shell mari,' differing in color, coarseness of grain, chemical composition, to any or ail of which the term 'silicious mari' would not be inappropriate. There is, however, no distinctive character which I could name that would separate any particular earth, as 'silicious mari,' from one hundred or one thousand other earths, differing from each other obviously in texture, color, and chemical composition. Infusorial earth is, on the other hand, characterized by the presence in it of the infusorial shields, so-called, recognizable by the microscope, From the fact that maris of ail kinds are sediments from water, and that infusorial plants inhabit and perish in water, most maris contain more or less infusorial shields, so that silicious maris and infusorial earth cannot commonly be sharply discrimi- nated. �"Quartz, chemically, îs oxide of silicon. It contains no hydrogen, and yields no water when heated; its specifie grav- ity is 2.65 ; it will not readily dissolve in a boiling aqueous solution of potash or soda, even when finely pulyerized. This specimen of infusorial earth, (Exhibit M,) which consista very largely of the skeletons of microscopic plants, is chemically oxide of silicon plus water, and when heated gives ofif several per cent, of water. Its specifie gravity is less than that of quartz ; it is softer than quartz ; it dissolves with the greatest «ase, to a large extent, in a boiling aqueous solution of potash ����