DIVISIBILITY. 



695 



mer, till they acquire a breadth of more than three 

 inches, and are therefore extended ten times. These 

 are again quartered, and placed between the folds 

 df gold-beaters' skin, and stretched out, by the 

 operation of a lighter hammer, to the breadth of five 

 inches. The same process is repeated, sometimes 

 more than once, by a succession of lighter hammers ; 

 so that 376 grains of gold are thus finally extended 

 into 2000 leaves of 3 3 inches square, making in all 

 eighty books, containing each twenty-five leaves. 

 The metal is, consequently, reduced to the thinness 

 of the 282,000th part of an inch, and every leaf 

 weighs rather less than the 5th part of a grain. Sil- 

 ver is likewise capable of being laminated, but will 

 scarcely bear an extension above hah that of gold, or 

 the 150,000th part of an inch thick. Copper and tin 

 have still inferior degrees of ductility, and cannot, 

 perhaps, be beat thinner than the 20,000th part of 

 an inch. These form what is called Dutch leaf. 



In the gilding of buttons, five grains of gold, which 

 is applied as an amalgam with mercury, is allowed 

 to each gross ; so tliat the coating left must amount 

 to the 1 10,000th part of an inch in thickness. If a 

 piece of ivory or white satin be immersed in a nitro- 

 muriate solution of gold, and then plunged into a jar 

 of hydrogen gas, it will become covered with a sur- 

 face of gold hardly exceeding in thickness the 

 10,000,000th part of an inch. The gilt wire used 

 in embroidery is formed by extending gold over a 

 surface of silver. A silver rod, about two feet long 

 and an inch and a half in diameter, and therefore 

 weighing nearly twenty pounds, is richly coated with 

 about 800 grains of pure gold. In England, the 

 lowest proportion allowed is 100 grains of gold to 

 a pound of silver. This gilt rod is then drawn 

 through a series of diminishing holes, till it lias 

 stretched to the vast length of 240 miles, when the 

 gold has. consequently, become attenuated 800 times, 

 each grain covering a surface of 9600 square inches. 

 This wire being now flattened, the gulden film suffers 

 a further extension, and has its^Bckness reduced to 

 the four or five millionth part ot an inch. 



It has been asserted, that fores of pure gold can 

 be drawn of only the 4000th part m an inch in 

 diameter. But Dr W. H. Wollaston, by an ingenious 

 process, has lately advanced much furthei% Taking 

 a short cylinder of silver, about the third part of an 

 inch in diameter, he drilleda fine hole through its 

 axis, and inserted a wire ori|atinum, only the 100th 

 part of an inch thick. ThisVsJlyer mould was now 

 drawn through the successive holes of a steel plate, 

 till its diameter was brought to near the 1500th part 

 of an inch, and, consequently, the internal wire, being 

 diminished in the same proportion, was reduced to 

 between the four and five thousandth part of an inch. 

 The compound wire was then dipped in warm nitric 

 acid, which dissolved the silver, and left its core, or 

 the wire of platinum. By passing the incrusted 

 platinum through a greater number of holes, wires 

 still finer were obtained, some of them onlyTnH 

 30,000th part of an inch in diameter. The tenacity 

 of the metal, before reaching that limit, was considy 

 erable ; a platinum wire of the 18,000th part of an 

 inch in diameter, supporting the weight of one graini 

 and a third. 



Such excessive fineness is hardly surpassed by the 

 filamentous productions of nature. Human hair 

 varies in thickness, from the 250th to the 600th part 

 of an inch. The fibre of the coarsest wool is about 

 the 500th part of an inch ii diameter, and that of the 

 finest only the 1500th part. The silk line, as spun 

 by the worm, is about the 5000th part of an inch 

 thick ; but a spider's line is, perhaps, six times finer, 

 or only the 30,000th part of an inch in diameter ; in- 

 somuch, that a single pound of this attenuated sub- 



stance might be sufficient to encompass our globe. 

 The red globules of the human blood have an irregu- 

 lar, roundish shape, from the 2500th to the 3300th of 

 an inch in diameter, with a dark central spot. 



The trituration and levigation of powders, ana the 

 perennial abrasion and waste of the surface of solid 

 bodies, occasion a disintegration of particles, almost 

 exceeding the powers of computation. Emery, after 

 it lias been ground, is thrown into a vat filled with 

 water, and the fineness of the powder is distinguished 

 by the time of its subsidence. In very dry situations, 

 the dust lodged near the corners and crevices of an- 

 cient buildings is, by the continual agitation of the 

 air, made to give a glossy polish to the interior side 

 of the pillars, and the less prominent parts of those 

 venerable remains. So fine is the sand on the adust 

 plains of Arabia, that it is carried sometimes 300 

 miles over the Mediterranean, by the sweeping si- 

 rocco. Along the shores of that sea, the rocks are 

 peopled by the pholas, a testaceous and edible worm, 

 which, though very soft, yet, by unwearied persever- 

 ance, works a cylindrical hole into the heart of the 

 hardest stone. The marble steps of the great churches 

 in Italy are worn by the incessant crawling of abject 

 devotees ; nay, the hands and feet of bronze statues 

 are, in the lapse of ages, wasted away by the ardent 

 kisses of innumerable pilgrims that resort to those 

 shrines. What an evanescent pellicle of the metal 

 must be abraded at each successive contact! 



The solutions of certain saline bodies, and of other 

 coloured substances, exhibit a prodigious subdivision 

 and dissemination of matter. A single grain of the 

 sulphate of copper, or blue vitriol, will communicate 

 a fine azure tint to five gallons of water. In this case, 

 the copper must be attenuated at least ten million 

 times; yet each drop of the liquid may contain as 

 many 'coloured particles, distinguishable by our un- 

 assisted vision. A still minuter portion of cochineal, 

 dissolved in deliquiate pojgsh, will strike a bright 

 purple colour through an equal mass of water. 



Odours are capable of a much wider diffusion. A 

 single grain of musk has been known to perfume a 

 large room for the space of twenty years. Consider 

 how often, during that time, the air of the apartment 

 must nave been renewed, and have become charged 

 with fresh odour ! At the lowest computation, the 

 musk had been subdivided into 320 quadrillions of 

 particles, each of them capable of affecting the olfac- 

 tory organs. The vast diffusion of odorous effluvia 

 may be conceived from the fact, that a lump of assa- 

 fcetida, exposed to the open air, lost only a grain in 

 seven weeks. Yet, since dogs hunt by the scent 

 alone, the effluvia emitted fiom the several species 

 of animals, and from different individuals of the same 

 fface, must be essentially distinct. The vapour of 

 pestilence conveys its poison in a still more subtile 

 and attenuated form. The seeds of contagion are 

 known to lurk, for years, in various absorbent sub- 

 stances, which scatter death on exposure to the air. 



But tht' diffusion of the particles of light defies all 

 powers of calculation. A small taper will, in a 

 twinkling, illuminate the atmosphere to the distance 

 of four miles ; yet the luminous particles which fill 

 that wide concavity cannot amount to the five thou- 

 siindth juut of a grain, which may be the whole con- 

 sumption of the wax in light, smoke, and ashes. 



Animated matter likewise exhibits, in many in- 

 stances, it wonderful subdivision. The milt of a 

 codfish, when it begins to putrefy, has been computed 

 to contain a billion of perfect insects ; so that thou- 

 sands of these living creatures could be lifted on the 

 point of a needle. But the infusory animalcules dis- 

 play, in their structure and functions, the most tran- 

 scendent attenuation of matter. The vibrio undula, 

 found in duck-weed, is computed to be ten thousand 



