That therefore this metal thus received hath any undeniable effect, we shall not imperiously determine, although, beside the former experiments, many more may induce us to believe it. But, since the point is dubious and not yet authentically decided, it will be no discretion to depend on disputable remedies; but rather, in cases of known danger, to have recourse unto medicines of known and approved activity. For, beside the benefit aceruing unto the sick, hereby may be avoided a gross and frequent error, commonly committed in the use of doubtful remedies conjointly with those which are of approved virtues, that is, to impute the cure unto the conceited remedy, or place it on that whereon they place their opinion; whose operation, although it be nothing, or its concurrence not considerable, yet doth it obtain the name of the whole cure, and carrieth often the honour of the capital energy, which had no finger in it.

Herein exact and critical trial should be made by public enjoinment, whereby determination might be settled beyond debate; for, since thereby not only the bodies of men, but great treasures might be preserved, it is not only an error of physics, but folly of state, to doubt thereof any longer.1

4. That a pot full of ashes will still contain as much water as it would without them, although by Aristotle in his problems taken for granted, and so received by most, is not effectable upon the strictest experiment I could ever make. For when the airy interstices are filled, and as much of the salt of the ashes as the water will imbibe is dissolved, there remains a gross and terreous portion at the bottom, which will possess a space by itself, according whereto, there will remain a quantity of water not receivable: so will it come to pass in a pot of salt, although decrepitated:2 and so also in a pot of snow; for so much it will want in reception, as its solution taketh up, according unto the bulk whereof, there will remain a portion of water not to be admitted: so a was either by letting wine stand for a certain time in it, or (if it was required to antimonize more wine than the cup would contain), by plunging the cup into the requisite quantity of wine. Regulus of antimony was also anciently used in the form of pills, which, it is asserted, were, by some frugal persons, re-employed as often as they could be

recovered!

1 Herein, &c.] Added in the 2nd edition.

2 decrepitated.] Calcined till it has ceased to crackle.

glass stuffed with pieces of sponge will want about a sixth part of what it would receive without it: so sugar will not dissolve beyond the capacity of the water, nor a metal in aqua fortis be corroded beyond its reception; and so a pint of salt of tartar, exposed unto a moist air until it dissolve, will make far more liquor, or, as some term it, oil, than the former measure will contain..

Nor is it only the exclusion of air by water, or repletion of cavities possessed thereby, which causeth a pot of ashes to admit so great a quantity of water, but also the solution of the salt of the ashes into the body of the dissolvent: so a pot of ashes will receive somewhat more of hot water than of cold, for the warm water imbibeth more of the salt; and a vessel of ashes more than one of pin-dust or filings of iron; and a glass full of water will yet drink in a proportion of salt Sor sugar without overflowing.

Nevertheless, to make the experiment with most advantage, and in which sense it approacheth nearest the truth, it must be made in ashes thoroughly burnt and well reverberated by fire, after the salt thereof hath been drawn out by iterated decoctions. For then the body, being reduced nearer unto earth, and emptied of all other principles, which had former ingression unto it, becometh more porous, and greedily drinketh in water. He that hath beheld what quantity of lead the test of saltless ashes will imbibe, upon the refining of silver, hath encouragement to think it will do very much more in water.3

5. Of white powder, and such as is discharged without report,4 there is no small noise in the world; but how far agreeable unto truth, few, I perceive, are able to determine. Herein therefore, to satisfy the doubts of some and amuse

3. Nevertheless, &c.] Added in 2nd edition.

45 Of white powder, &c.] The nearest approach to white powder is the fulminating powder, in which carbonate of potash is substituted for charcoal: the composition being three parts of nitre, two of carbonate of potash, and one of sulphur.-Ure's Dictionary of Chemistry.

But this detonates more loudly than gunpowder. The error which it was our author's object to correct here, was that of expecting an effective gunpowder (of whatever colour) which should be "without report." He justly observes, that, even admitting the probability of making a "white powder,"-"and such an one as may give no report," it would "be of little force, and the effects thereof no way to be feared."

the credulity of others, we first declare, that gunpowder consisteth of three ingredients, saltpetre, small-coal, and brimstone.5 Saltpetre, although it be also natural and found in several places, yet is that of common use an artificial salt, drawn from the infusion of salt earth, as that of stales, stables, dove-houses, cellars, and other covered places, where the rain can neither dissolve, nor the sun approach to resolve it: brimstone is a mineral body of fat and inflammable parts, and this is either used crude, and called sulphur vive, and

5

we first declare, &c.] The account here given of gunpowder is upon the whole accurate; especially if we allow for the unsettled state of philosophical language at that time, which makes it sometimes difficult to feel assured of Sir Thomas's precise meaning. He was evidently aware of the necessity of employing pure ingredients in the composition of gunpowder; observing that "powder which is made of impure and greasy petre hath but a weak emission, and giveth a faint report;" and again, that the best way to alter the noise and strength of the discharge, consists in the quality of the nitre." He assigns, with sufficient correctness, to its constituents their respective share in the general results, when he ascribes to the charcoal the "quick accen sion [ignition]" to the sulphur the "piercing and powerful firing," and to the nitre the "force and the report."-Modern experiment has shown that the detonation or explosion of gunpowder is attributable to the nitre, when combined with inflammable substances, viz. the sulphur and charcoal; and arises from the sudden extrication, by combustion, of nitrogen and carbonic acid gases, which expand to a volume about two thousand times greater than that originally occupied by the powder.The opinions of Carden and Snellius, quoted by our author, as to the degree of expansion, are erroneous. In describing the mixture of the three ingredients of gunpowder, Sir Thomas has named proportions very different from those now adopted. Barrow informs us, that the Chinese soldiery make their gunpowder (for it is there the duty of every soldier to prepare his own) in the proportion of 50lbs. of nitre to 25lbs. each of sulphur and charcoal: but the modern practice is to employ about 75 of nitre and 15 (or 16) of charcoal to 10 (or 9) of sulphur; varying the relations between the two last, according as the object is to produce a powder of greater durability or of greater strength; more usually the sulphur has been increased, and the carbon lessened in order to obtain a more lasting article, by a slight sacrifice of strength-which may readily be compensated by increasing the charge.

Saltpetre, although it be also natural, &c.] Native saltpetre, or nitre (nitrate of potash) occurs in crusts and capillary crystals, in Spain, France, Italy, and Hungary; in Arabia, Persia, and India; at the Cape of Good Hope, in the mountains of Kentucky, and near Lima in South America. But not being naturally produced in sufficient quantity, is obtained artificially, in what are termed nitre-beds, as is described by Thenard (Traité de Chimie, ii. 511.)

of a sadder colour, or, after depuration, such as we have in magdaleons or rolls, of a lighter yellow: small-coal is known unto all, and for this use is made of sallow, willow, alder, hazel, and the like:—which three, proportionably mixed, tempered, and formed into granulary bodies, do make up that powder which is in use for guns.

Now all these, although they bear a share in the discharge, yet have they distinct intentions, and different offices in the composition. From brimstone proceedeth the piercing and powerful firing; for small-coal and petre together will only spit, nor vigorously continue the ignition. From smallcoal ensueth the black colour and quick accension; for neither brimstone nor petre, although in powder, will take fire like small-coal, nor will they easily kindle upon the sparks of a flint; as neither will camphor, a body very inflammable; but small-coal is equivalent to tinder, and serveth to light the sulphur; it may also serve to diffuse the ignition through every part of the mixture; and being of more gross and fixed parts, may seem to moderate the activity of saltpetre, and prevent too hasty rarefaction.8 From saltpetre proceedeth the force and the report; for sulphur and smallcoal mixed will not take fire with noise or exilition,9 and powder which is made of impure and greasy petre hath but a weak emission, and giveth a faint report. And therefore, in the three sorts of powder, the strongest containeth saltpetre, and the proportion thereof is about ten parts of petre unto one of coal and sulphur.

But the immediate cause of the report is the vehement commotion of the air, upon the sudden and violent eruption of the powder; for that being suddenly fired, and almost altogether, upon this high rarefaction requireth by many degrees a greater space than before its body occupied; but finding resistance, it actively forceth his way, and by concussion of the air occasioneth the report. Now with what

7 small-coal.] The old term for charcoal. For magdaleon, see note at p. 150.

it may also, &c.] Added in 2nd edition. That charcoal serves as a diffusing medium to facilicate ignition is true; but it is not easy to see how it can operate to "moderate the activity of saltpetre."

9

exilition.]

The act of springing out suddenly." The present passage is Johnson's sole authority.

VOL. I.

N

violence it forceth upon the air, may easily be conceived, if we admit, what Cardan affirmeth, that the powder fired doth occupy an hundred times a greater space than its own bulk; or rather what Snellius more exactly accounteth, that it exceedeth its former space no less than 12,500 times. And this is the reason not only of this fulminating report of guns, but may resolve the cause of those terrible cracks, and affrighting noises of heaven; that is, the nitrous and sulphureous exhalations, set on fire in the clouds; whereupon requiring a larger place, they force out their way, not only with the breaking of the cloud, but the laceration of the air about it. When, if the matter be spirituous, and the cloud compact, the noise is great and terrible: if the cloud be thin, and the materials weak, the eruption is languid, ending in corruscations and flashes without noise, although but at the distance of two miles; which is esteemed the remotest distance of clouds.2 And, therefore, such lightnings do seldom

1 And this is the reason, &c.] In his comparison of gunpowder with lightning, our author proposes an opinion which was maintained by his great contemporary, Dr. Wallis; who considered their effects so similar, that they might, without hesitation, be ascribed to the same cause. The discovery of electricity, and the identity of lightning with the electric fluid, was reserved for a century later :-but the philosophy of sound is substantially the same in both cases; for, although the immediate results of the ignition of gunpowder and of the discharge of electric fluid, are directly opposite,- being rarefaction in the one case, by the evolution of gases, and in the other condensation by the combination of other gases; and although the first results on the surrounding atmosphere are also opposite, the air in the latter case advancing in order to occupy the vacuum created by condensation, and in the former retreating in order to afford the space required by rarefaction;-yet, the subsequent results in both cases are, alternate reactions of the particles of air, till its average density is regained. Hence it follows, that in both cases sound arises from the concussion, and consequent undulation (to use Professor Brande's term) occasioned by the respective explosion of gunpowder and of lightning.

If it be admitted, however, that the ideas of Sir Thomas on the point were not far from the truth; it must, on the other hand, be confessed that he has clothed them in language not only unphilosophical, but most ambiguous, when he speaks of "the breaking of the clouds, and lacera tion of the air,"—and of "the matter being spirituous, and the clouds compact; or "the clouds thin and the materials weak."

2 the remotest distance of clouds.] The average height of clouds scarcely exceeds a mile, or a mile and half. And many (especially