[Sidenote: Granite.] III. GRANITE, LIMESTONE AND MARBLE.--What is here called granite is really syenite. It is found high on the mountains, associated, as already intimated, with the magnetic iron ore, and with hard quartzite, porphyry, epidote, hornblende, and limestone largely marbleized. This group of rocks forms the core of the Cascade Mountains, and hence underlies all the coal-bearing rocks to the westward. The group has been assigned by some geologists to the Archæan age; but it is possible that they are metamorphosed strata of the Silurian, or some subsequent period. Some of this syenite has a large proportion of quartz, which gives it a light appearance; but in other places the hornblende crystals are of good size and in full proportion, and the feldspar is of the orthoclase variety, which gives a mixture of three colors, and makes fully as handsome a stone as the Quincy granite. Limestone is reported as existing in some of the islands in Puget Sound, where it is burnt into lime; but I have met with no particular account of it. [Sidenote: Marble and limestone.] The limestone and marble associated with the iron ore on the Cascade Mountains has already been alluded to. It is of fine quality, very abundant, and easily quarried. It will have great value for flux and commercial lime. It is also beautiful in color, varying from the purest white to blue, and mixtures of the two colors. In texture it is sometimes exceedingly fine grained, and in others crystallized into a true and beautiful marble, which, so far as can be judged by eye, would be well adapted to both inside and outside finishing and statuary. On Mount Logan the limestone deposit almost covers the mountain above the lower line of the iron ore, and is so exposed as to be quarried with the greatest ease. The same association of limestone in heavy beds with iron ore seems to exist also on the Cle-ellum, as mentioned by Mr. Burch. This gentleman spoke to me, also, of a very beautiful and easily burned limestone in the Wenatchie Valley. Large beds of limestone also exist in connection with the precious and base metals, which are next to be described. In the Colville country limestone seems to abound. [Sidenote: Precious metals on Cascade Mountains.] IV. THE PRECIOUS AND BASE METALS.--In the Cascade Mountains, and in the mountains north of the plateau country of East Washington, and in the Coeur d'Alene Mountains, within the border of Idaho, occur numerous veins bearing gold, silver, copper, lead, sulphur and iron. Discoveries on Cascade Mountain proper have been made on both sides, chiefly in the region of the iron ore. Those at the Denny and Chair Peak mines have been most spoken of. Professor Mason, of the "Rennselaer Polytechnic Institute," Troy, New York, gives the following assay of two samples sent from the Chair Peak claim of Kelly, Wilson & Co.: 1st. Silver 13.9 oz. per ton. 2d. Silver 12.4 Both 14% copper.