KOCKS : THEIR CONSTITUENTS AND KINDS. 76 



18-71 per ceut ; of Eq. Telmateia, 26-75 per cent; of Conifers, mostly less than 2 per 

 cent ; of Fungi, 3-10 to 9-5 per cent ; of Lichens, 1-14 to 17 per cent (the last in Clado- 

 nia), but mostly between 1-14 and 4-30 per cent. In Lycopodium dendroideum, Hawes, 

 in his analyses (p. 362), found 3-25 per cent of ash; in L. complanatum, 5-47 per cent, 

 and in Equisetum hyemale, 11-82 per cent. 



Lycopodium chamcBcyparissus afforded Aderholt 51 -85 per cent of alumina ; or, when 

 without spores, 57-36 per cent ; while Ritthausen obtained 39-97 alumina for this species, 

 and 37-87 for L. coviplanatum. In Lycopods the silica constitutes 10 to 14 per cent of 

 the ash. In the ash of Mosses have been found 8 to 23-58 per cent of potash, 4 to 16 of 

 silica, 1-06 to 6-56 of phosphoric acid, 4-9 to 10-7 of magnesia. Among Ferns, the amount 

 of ash, so far as determined, varies from 5 to 8 per cent. 



The ash of Fungi affords 21 to 54 per cent of potash, 0-36 to 11-8 of soda, 1-27 to 8 

 of magnesia, 15 to 60 of phosphoric acid, and to 15-4 of silica. Among Lichens, the 

 ash of Cladonia rangiferina contains 70-34 per cent of silica ; of other species, less, down 

 to 0-9 per cent. 



Trapa nutans, of bogs, in Europe, affords 13 to 25 per cent of ash ; and 25 per cent 

 of this is oxide of iron (Fe203) with a little oxide of manganese. Of the ash of the fruit 

 scales, over 60 per cent is oxide of iron. The Ilex cassine of North Carolina (the leaves 

 of which produced the Black Drink of the Indians) afforded, from leaves collected in May 

 and dried, 5-75 per cent of ash, which is remarkable (No. 11, above) for the amount of 

 potash and magnesia. Another Holly afforded 11-39 of magnesia, and 12-34 of lime. 



Ash of bean straw (6 to 7 per cent of dried) affords 35 to 45 per cent of potash ; of 

 buckwheat straw (6-15 per cent), 46-6 of potash ; of oat straw (5-1 per cent), 22 per cent 

 of potash. 



Soda is a prominent constituent in the ash of Sea-weeds {Fuci), analysis giving 14*39 

 per cent of ash, and in this, 24 of soda, with 14-5 of potash. Scirpus (bulrush) afforded 

 8-65 per cent ash, and in it 10-3 per cent of soda with 9-7 of potash; and Juncus, 6-6 

 of soda to 36-6 of potash. The ash of beets contains 14-8 per cent of soda; of carrots, 

 22-1 per cent ; but grasses generally 1 to 5 per cent of soda. 



The amount of sulphur in the ash of grasses, straws, and woods is usually 1 to 2 -5 per 

 cent ; in that of Fucus, 18 per cent ; in that of common vegetables, 3 to 6 per cent. The 

 amount of chlorine in the ash of grasses is 3 to 5-5 per cent ; in that of vegetables, 3 to 11 

 per cent ; in that of Fucus, 10 per cent ; in that of Juncus, 14-2 per cent ; in that of woods, 

 usually less than 1 per cent. (These percentages are taken from tables in Johnson's How 

 Crops Grow, New York, 1887.) 



Kinds of Rocks. 



(1) General explanations. — Eocks are conveniently divided into two 

 general sections : (1) the Fragmental or Clastic, and (2) the Crystalline. 



For the study of even the coarser kinds of rocks, the geological student should have 

 a pocket lens. In investigation, it will generally be necessary to supplement this w'th 

 a compound polariscope-microscope made especially for the study of rocks ; but a thor- 

 ough study of the elements of petrology is required for the satisfactory use of the latter 

 instrument. 



Fragmental Rocks. — The fragmental rocks are those that have been 

 made out of fragments of older rocks. They are also called clastic rocks, 

 from the Greek for to break. All the sand, gravel, stones, earth, mud, and 

 clay of the world is worn or pulverized or decomposed rock. Each grain, 

 however small or large, may hence be spoken of as a fragment of preexist- 

 ing rocks. The rocks of an age are mostly made out of the detritus (worn- 

 out rocks) of preceding time. 



