592 



SUPPLEMENT 



get motion in such a host of atoms, and that 

 tlieir activity may be indefinitely prolonged. 

 We shall again refer to the activity of mole- 

 cules when we come to speak of infusorial and 

 spermatic animalcules whose movements they 

 greatly resemble. 



Ores and minerals should first be examined 

 in very small portions in their native state ; 

 as their complex structure cannot be so well 

 understood from an artificial crystallization, 

 which rather developes primitive forms and 

 elementary principles. The crystalline for- 

 mations and foliations of any mineral may be 

 subjected to microscopic examination, by dis- 

 solving a few particles in muriatic or nitric 

 acid. It would answer no purpose to enter 

 into an extended description of the crystalline 

 structures of minerals, as exhibited under the 

 microscope ; since these can only be adequately 

 comprehended from actual observation, or from 

 very elaborate illustrative engravings. We 

 shall therefore confine ourselves to the mention 

 of a variety of minute native bodies discovered 

 by various observers. 



On the sea shore, along the banks of rivers, 

 and in many inland places, various species of 

 sand are discovered, widely differing from 

 each other, and all exhibiting a beauty of 

 structure and finish well worthy of observation. 

 " These species differ in colour, figure and 

 size ; and as among stones some are called 

 precious for their excellency, so also amongst 

 sands there are some that deserve the same 

 epithet for their beauty. The grains of sea- 

 sand are very large, and afford great variety 

 of all shapes and colours, both opaque and 

 transparent. River sands are smaller grained, 

 of different colours and forms ; and the in- 

 land, or pit sands, vary also exceedingly, 

 being some white, some brown, some yellow, 

 &c." " These varieties are very agreeable to 

 examine by the microscope, which shows, in 

 some of the shining kinds, grains having all 

 numbers of sides and angles, and so finely 

 polished, that no diamond is more exquisitely 

 beautiful. On others, grotesque figures, or 

 representations of landscapes, buildings, plants 

 and animals at once surprise and please." 

 There are several kinds of black sand brought 

 from the East Indies, and also from Virginia 

 and other parts of America, which exhibit 

 beautifully polished surfaces, and may be 

 attracted by the load-stone. A red-coloured 

 sand is also brought from abroad (we believe 

 from Africa) which presents a delightful pic- 

 ture under the magnifier, resembling a heap 

 of gems carelessly thrown together. 



Small, irregularly shaped particles of the 

 precious stones, are very interesting micro- 

 scopic objects. Leuwenhoeck's method of 

 examining the diamond, and the phenomena 

 it presented, are thus described by Baker. 



" He broke a small one between two hammers, 

 and placing the pieces before his microscope. 

 in the sun-shine, he saw many sparkling 

 flames issue from them, with a continual cor- 

 ruscation, in some, like faint lightning. 

 Then viewing them in the shade, he observed, 

 among other pleasing appearances, a little 

 flame that seemed to dart from each particle 

 of the diamond : and it was a glorious sight 

 to behold multitudes of sparkling flames, most 

 of a bright fire colour, and others greenish, 

 flashing faintly and like lightning at a dis- 

 tance. In other pieces of the diamond the 

 lamellae, or layers, were very plainly distin- 

 guished.'' This description is somewhat 

 grandiloquent, yet perfectly agrees with later 

 observations : the powerful refractions of this 

 gem and its structure are both very distinctly 

 developed by the microscope. Minute crystal- 

 line formations, vulgarly called diamonds, are 

 frequently found in the cavities of flint or 

 rock ; these vary considerably in form, and 

 by their action on the rays of light become 

 objects of great interest to the microscopical 

 observer. Sir David Brewster has called 

 attention to the singularly shaped microscopic 

 cavities in gems and other mineral bodies, 

 " containing two fluids unknown to the 

 chemist, groups of crystals, floating balls, and 

 exhibiting actual chemical operations going 

 on in these minute laboratories when exposed 

 to changes of temperature. In some of the 

 precious stones, particularly in diamond, 

 garnet, &c., these cavities are perfect spheres." 

 In his recent Treatise on the microscope, this 

 unwearied observer gives diagrams of " the 

 cavities containing the two new fluids that 

 will not mix, though in the same cavity ; " 

 and also of the beautiful spear-shaped cavities 

 formed in topaz. 



The examination of the inferior minerals, 

 such as common free-stone, &c., whilst it has 

 gratified the observer with a view of their 

 structure, has also developed serviceable truths 

 relative to the value and capabilities of the 

 materials in the ordinary concerns of life. 

 Their compactness or porosity, their durable 

 or perishable nature, may be determined with 

 much exactness by the aid of the microscope. 

 What is called Kettering stone (from the 

 locality of the quarry whence it is dug) is 

 shown, for example, to be eminently adapted 

 for filters, as it is composed of small globular 

 particles cohering so firmly together as to form 

 a substance harder then free-stone, yet is 

 filled with innumerable interstices arising 

 from the spherical surfaces touching only in 

 certain points. 



Before dismissing this portion of our sub- 

 ject, it may be interesting to transcribe the re- 

 marks of the old micrographers regarding the 

 minute globules of steel produced by the cora. 



