t of milk coagulation, and that of oil and unctious bodies only inencrassation. And, therefore, Aristotle makes a trial of the or tertility of human seed, from the experiment of congelation; edir that, saith he, which is not watery and improlifical will e not conglaciate: which, perhaps, must not be taken strictly, nabut in the germ and spirited particles; for eggs, I observe, thewill freeze in the albugineous part thereof. And upon this ground Paracelsus, in his Archidoris, extracteth the magisetery of wine; after four months' digestion in horse-dung, es exposing it unto the extremity of cold, whereby the aqueous parts will freeze, but the spirit retire, and be found unconangealed in the centre.

1

But whether this congelation be simply made by cold, or also by co-operation of any nitrous coagulum, or spirit of salt, the principle of concretion, whereby we observe that ice may be made with salt and snow by the fire-side, as is also observable from ice made by saltpetre and water, duly mixed and strongly agitated, at any time of the year, were a very considerable enquiry. For thereby we might clear the generation of snow, hail, and hoary frosts, the piercing quali

6 eggs, I observe, &c.] That point in the Chalaza, the spark of vivification, I wish it might freeze: it would rid my trees from caterpillars, which can continue their noxious species, by their hybernating eggs.Robinson's Endoxa.

7 or also by co-operation of any nitrous coagulum.] The doubt here expressed, whether the congelation of water is simply owing to cold, or whether the operation of cold may not be aided by saltpetre, or some analogous principle, is a remnant of the notions entertained of that salt by the alchemists, and the older operators in true chemistry who immediately succeeded them, of both whose ideas on such subjects our author retained a few, though (considering the state of science in his time) but very few indeed, and those of minor importance only. The arguments which he adduces in favour of this doubt are as fallacious as the supposition itself, which it involves, "That ice may be made with salt and snow by the fire-side," arises, not from any peculiar congealing virtue in the salt, but merely from the circumstance that the affinity it has for water produces a rapid liquefaction of the snow, which, robbing the surrounding bodies of their heat, in order itself to assume the liquid form (their sensible heat thus becoming latent in the resulting water) produces the cold. The case is similar with respect to the "ice made by saltpetre and water;" for here, the water subjected to experiment is reduced to the solid form by the abstraction of its sensible heat, consequent upon the liquefaction of the salt, in the solution of which it becomes latent.-Br.

ties of some winds, the coldness of caverns, and some cells. We might more sensibly conceive how saltpetre fixeth the flying spirits of minerals in chemical preparations, and how by this congealing quality it becomes an useful medicine in fevers.8

Again, the difference of their concretion is collectible from their dissolution, which being many ways performable in ice, is few ways effected in crystal. Now the causes of liquation are contrary to those of concretion; and, as the atoms and indivisible parcels are united, so are they in an opposite way disjoined. That which is concreted by exsiccation or expression of humidity, will be resolved by humectation, as earth, dirt, and clay; that which is coagulated by a fiery siccity, will suffer colliquation from an aqueous humidity, as salt and sugar, which are easily dissoluble in water, but not without difficulty in oil and well rectified spirits of wine. That which is concreted by cold, will dissolve by a moist heat, if it consist of watery parts, as gums arabic, tragacanth, ammoniac, and others, in an airy heat or oil, as all resinous bodies, turpentine, pitch, and frankincense; in both, as gummy resinous bodies, mastic, camphor, and storax; in neither, as neutrals, and bodies anomalous hereto, as bdellium, myrrh, and others. Some by a violent dry heat, as metals; which although corrodible by waters, yet will they not suffer a liquation2 from the powerfullest heat communicable unto that element. Some will dissolve by this heat,

8 But whether, &c.] This paragraph was added in Second Edition. 9 is few ways effected.] "Is not in the same manner effected."—Ed.

1646.

1 that which is concreted by exsiccation, &c.] The statements here made by our author respecting the causes of liquation and concretion, &c., are evidently derived from Aristotle, Met. lib. iv. cap. 6. See also the notes to Pseudodoxia, book i. chap. vi. p. 42.-Br.

2

yet will they not suffer a liquation.] Modern chemistry shows our author to be in error in his opinion, that heat of a peculiar nature is required for the fusion of metals. The only reason why the generality of metals connot be melted by hot water is, that they require a higher temperature for their liquefaction than can be given to that fluid under ordinary circumstances. But there is an alloy of bismuth, lead, and tin, which melts at a temperature inferior to that of boiling water, (commonly called on that account fusible metal), and which accordingly melts when immersed in that fluid. Under pressure, as when heated in Papin's digester for instance, water can be raised to a much higher

3

although their ingredients be earthy, as glass, whose materials are fine sand, and the ashes of kali or fern; and so will salt run with fire, although it be concreted by heat. And this way may be effected a liquation in crystal, but not without some difficulty, that is, calcination or reducing it by art into a subtle powder, by which way and a vitreous commixture, glasses are sometime made hereof, and it becomes the chiefest ground for artificial and factitious gems. the same way of solution is common also unto many stones and not only beryls and cornelians, but flints and pebbles are subject unto fusion, and will run like glass in fire.

But

;

But ice will dissolve in any way of heat, for it will dissolve with fire, it will colliquate in water, or warm oil, nor doth it only submit unto an actual heat, but not endure the potential calidity of many waters. For it will presently dissolve in cold aqua fortis, spirit of vitriol, salt or tartar, nor will it long continue its fixation in spirits of wine, as may be observed in ice injected therein.

Again, the concretion of ice will not endure a dry attrition without liquation; for if it be rubbed long with a cloth, it melteth. But crystal will calefy unto electricity, temperature than that at which it boils under the common pressure of the atmosphere; and thus can be made to melt lead, which is quite infusible in common boiling water.—Br.

3 glass.] In the Manchester Memoirs, vol. 2. p. 95, there are some interesting "Remarks on the Knowledge of the Ancients respecting Glass," by Dr. Falconer.

4 the concretion of ice will not endure a dry attrition, &c.] A similar exertion of ingenuity to that which has discovered a knowledge of the true chemical mixture of the atmosphere in certain mythological tales of the Egyptian priests, and of that of the constituents of water in some of the speculations of Lucretius, might, with far less aberration from the truth, affirm that in this sentence of our author is virtually an anticipation of Sir H. Davy's experiment, in which ice was melted by the mere friction of two pieces of it together. For as a cloth would be a very bad conductor of heat, the experiment of our author might, with care, be so made as to cause the fusion of the ice by the heat generated by the friction alone, independent of that which might (without care) be conducted from the hand of the experimenter through the cloth, and of that also which would be derived from the cloth itself, if not previously reduced to the freezing temperature. It is plain, also, from the author's use of the word "calefy" in the next period, that he believed the ice to be melted by the heat generated by the friction, and not by the friction alone, mechanically considered.-Br.

5 But crystal will calefy unto electricity.] It is an accurate observa

that is, a power to attract straws or light bodies, and convert the needle freely placed :—which is a declarement of very different parts, wherein we shall not enlarge, as having discoursed concerning such bodies in the chapter of electrics.

They are differenced by supernatation or floating upon water; for crystal will sink in water, as carrying in its own bulk a greater ponderosity than the space in any water it doth occupy, and will therefore only swim in molten metal and quicksilver. But ice will swim in water7 of what thinness soever; and, though it sink in oil, will float in spirits of wine or aqua vitæ. And therefore it may swim in water, not only as being water itself, and in its proper place, but perhaps as weighing somewhat less than the water it sesseth. And therefore, as it will not sink unto the bottom, so neither will it float above, like lighter bodies, but, being near in weight, lie superficially or almost horizontally

pos

tion that rock-crystal becomes electric by friction; but our author is mistaken in attributing the excitation of electricity to the heat produced by the friction. In this case, and in all others of electricity so excited, the agency of the friction appears to be merely mechanical. -Br.

6 They are differenced, &c.] They ; i. e. ice and crystal. Here again we have Ross's ingenious reply; it's no wonder to see a stone sink and ice swim; for crystal when it was ice, swimmed, being now a stone sinks; as being a body more compact, hard, solid, and ponderous; so a stick will swim, but when it is converted to a stone, it sinks. The argument therefore is good thus; crystal sinks, ice swims; therefore crystal is not ice; but it will not follow, therefore, crystal was not ice." -Arcana, p. 189.

66 some

7 But ice will swim in water.] The whole of this paragraph is excellent, in assertion as well as in argument, giving a very accurate view of the facts described. It is quite true that the ice weighs what less than the water it possesseth," specifically; that is, a bulk of ice equal to that of the water in its liquid form would weigh less than the water; and that this is the reason why it swims upon water. It is also true that ordinary ice is less compact, less continuous in its solidity than other crystalline bodies, and that it is full of spumes and bubbles, and" which abate its gravity." ." The last statement, that the freezing of water is at the same time condensation and rarefaction, is also correct: that its solid state must imply a kind of condensation, some sort of molecular approximation, is clear; and yet it expands in freezing, and thus unquestionably undergoes rarefaction.—Br.

8 somewhat less.] "No more."-Ed. 1646. The specific gravity of ice is to that of water, as 8 to 9. Its greater lightness was discovered by Galileo.

unto it. And therefore also, an ice or congelation of salt or sugar, although it descend not unto the bottom, yet will it abate, and decline below the surface in thin water, but very sensibly in spirits of wine. For ice, although it seemeth as transparent and compact as crystal, yet is it short in either;9 for its atoms are not concreted into continuity, which doth diminish its translucency; it is also full of spumes and bubbles, which may abate its gravity. And therefore, waters frozen in pans and open glasses, after their dissolution, do commonly leave a froth and spume upon them, which are caused by the airy parts diffused in the congelable mixture, which, uniting themselves, and finding no passage at the surface, do elevate the mass, and make the liquor take up a greater place than before: as may be observed in glasses filled with water, which, being frozen will seem to swell above the brim. So that if, in this condensation, any one affirmeth there is also some rarefaction, experience may assert it.1

They are distinguished, in substance of parts, and the accidents thereof: 2 that is, in colour and figure: for ice is a similary body, and homogeneous concretion, whose material is properly water, and but accidentally exceeding the simplicity of that element. But the body of crystal is mixed, its ingredients many, and sensibly containeth those principles into which mixed bodies are reduced. For beside the spirit and mercurial principle,3 it containeth a sulphur or inflam

9 yet is it short in either.] "Yet is it inferior to crystal, both in transparency and compactness."

1 which are, &c.] From 1. 11 to the end of the paragraph was added in 2nd Edit.

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2 They are distinguished, &c.] Ross again meets the author on the hypothesis, that no present difference between ice and crystal can prove that the one may never have been the other. 'Crystal is not so much distinguished either in substance or accidents from ice, as a chick is from an egg, and yet the chick was an egg."-Arcana, 190.

3 For besides the spirit and mercurial principle, &c.] Our author's notions of the chemical nature of rock-crystal are those of the alchemists, and are wholly unfounded. There is neither spirit, mercury, nor sulphur, in rock-crystal; at least, nothing to which those appellations can properly be applied: it is silica, or the earth of flints, in a pure crystallized form, itself composed of equal weights of silicon (a single combustible substance), and oxygen. It may be suspected, with some plausibility, however, that the notion of the alchemists, that