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Updated: June 6, 2025
As his account of the cultivation of pyrethrum is the best we know of we quote here his experience in full, with but few slight omissions: "The soil best adapted to its culture should be composed of pure ground, somewhat silicious and dry. Moisture and the presence of clay are injurious, the plant being extremely sensitive to an excess of water, and would in such case immediately perish.
The polishing and sharpening are done in several stages: the first stage usually by rubbing the blade upon a block of sandstone; the second stage by the use of a hone of finer grain; and the highest polish is attained by rubbing with a leaf whose surface is hard and probably contains silicious particles. At the present time imported files are much used.
Jacini says: "A large proportion of the water of the lakes, instead of discharging itself by the Ticino, the Adda, the Oglio, the Mincio, filters through the silicious strata which underlie the hills, and follows subterranean channels to the plain, where it collects in the fontanili, and being thence conducted into the canals of irrigation, becomes a source of great fertility."
I could see nothing peculiar in this gravel; some silicious pebbles as large as a pigeon's egg, pieces of white and reddish quartz, iron stone, and killow, and a soft friable yellow stone, which crumbled to pieces by the fingers, were the chief minerals that I could distinguish. Besides the above there was a great portion of sand, and a yellow earth resembling till.
This makes up one-quarter of the crust, leaving only one-quarter to be accounted for. Silicon mixed with oxygen makes silica or quartz. There are few rocks which have not a large amount of quartz in them. Common flint, sandstones, and the sand of our shores, are made of quartz, and therefore belong to the first class of Silicious or Flint Rocks. Granites and lavas are about one-half quartz.
The peak of Maunganamu was only one of the many cones which bristle on this part of the island. It was a volcano of the future. A slight mechanical change would produce a crater of eruption in these slopes, which consisted merely of whitish silicious tufa.
The species of Diatoms entering into this deposit have not yet been worked up, but they appear to be referable chiefly to the genera Fragillaria, Coscinodiscus, Choetoceros, Asteromphalus, and Dictyocha, with fragments of the separated rods of a singular silicious organism, with which we were unacquainted, and which made up a large proportion of the finer matter of this deposit.
The silicious incrustations left by the overflow from the large pool had made a series of terraces, two to six feet high, with the appearance of being hewn from white or pink marble; each of the basins containing a similar azure water.
Rhododendron intermedium is an intermediate form between the hairy and the rusty species from the Swiss Alps, R. hirsutum and R. ferrugineum, the former growing on chalky, and the other on silicious soils.
It is a known fact that these worms have existed for days together in the nostrils, throat, and stomach of man, causing inexpressible pain and, finally, death. Gemelli Careri has already mentioned them. I discovered similar formations, of extraordinary beauty and extent, in the great silicious beds of Steamboat Springs in Nevada.
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