# Reflections upon Ancient and Modern Learning/Chapter 15

CHAP. XV.
Of several Instruments invented by the Moderns, which have helped to advance Learning.
HAving now enquired into the State of Mathematicks, as they relate to Lines and Numbers in general, I am next to go to those Sciences which consider them as they are applied to Material Things. But these being of several Sorts, and of a vast Extent, taking in no less than the whole Material World, it ​ought to be observed, that they cannot be brought to any great Perfection, without Numbers of Tools, or Arts, which may be of the same Use as Tools, to make the Way plain to several Things, which otherwise, without their Help, would be inaccessible.
Of these Tools, or Instruments, some were anciently invented, and those Inventions were diligently pursued: Others are wholly new. According to their Uses, they may be ranged under these two General Heads: (1.) Those which are useful to all Parts of Learning, though perhaps not to all alike. (2.) Those which are particularly subservient to a Natural Philosopher, and a Mathematician. Under the first Head one may place Printing, and Engraving. Under the Latter come Telescopes, Microscopes, the Thermometer, the Baroscope, the Air-Pump, Pendulum-Clocks, Chymistry, and Anatomy. All these, but the two last, were absolutely unknown to former Ages. Chymistry was known to the Greeks, and from them carried to the Arabs. Anatomy is, at least, as old as Democritus and Hippocrates; and among the exact Epyptians, something older.
The Use of Printing has been so vast, that every thing else wherein the Moderns ​have pretended to excel the Ancients, is almost entirely owing to it: And withal, its general Uses are so obvious, that it would be Time lost to enlarge upon them; but it must be taken Notice of, because Sir William Temple has questioned (m)(m) Pag. 6. whether Printing has multiplied Books, or only the Copies of them, from whence he concludes, that we are not to suppose that the Ancients had not equal Advantages by the Writings of those that were ancient to them, as we have by the Writings of those that are ancient to us. But he may easily solve his own Doubt, if he does but reflect upon the Benefit to Learning which arises from the multiplying Copies of good Books: For though it should be allowed, that there were anciently as many Books as there are now, which is scarce credible, yet still the Moderns have hereby a vast Advantage, because, (1.) Books are hereby much cheaper, and so come into more Hands. (2.) They are much more easily read; and so there is no Time lost in poring upon bad Hands, which wastes Time, wearies the Reader, and spoils Mens Eyes. (3.) They can be printed with Indexes, and other necessary Divisions, which, though they may be made in MSS. yet they will make them so voluminous and cumber​some, that not one in Forty who now mind Books, because they love Reading, would then apply themselves to it. (4.) The Notice of new and excellent Books is more easily dispersed. (5.) The Text is hereby better preserved entire, and is not so liable to be corrupted by the Ignorance or Malice of Transcribers; this is of great Moment in Mathematicks, where the Alteration of a Letter, or a Cypher, may make a Demonstration unintelligible. But to say more upon this Subject would be to abuse Mens Patience, since these things, if not self-evident, yet need no Proof.
Engraving upon Wood, or Copper, is of great Use in all those Parts of Knowledge where the Imagination must be assisted by sensible Images. For want of this noble Art, the Ancient Books of Natural History and Mechanical Arts, are almost every where obscure; in many Places unintelligible. Mathematical Diagrams, which need only a Ruler and a pair of Compasses, have been better preserved, and could with more Ease be drawn: But in Anatomy, in Mechanicks, in Geography, in all Parts of Natural History, Engraving is so necessary, and has been so very advantageous, that without it, many of those Arts and Sciences would to this ​Hour have received very little Increase. For when the Images, the Proportions, and the Distances of those things wherein a Writer intends to instruct his Reader, are fully and minutely engraven in Prints, it not only saves Abundance of Words, by which all Descriptions must of Necessity be obscured, but it makes those Words which are used, full and clear; so that a skillful Reader is thereby enabled to pass an exact Judgment, and can understand his Authors without a Master, which otherwise it would be impossible to do; so as to be able to discern all, even the minutest Mistakes and Oversights in their Writings, which puts an end to Disputes, and encreases Knowledge.
These are general Instruments, and more or less serviceable to all sorts of learned Men in their several Professions and Sciences: Those that follow are more particular: I shall begin with those that assist the Eye, either to discern Objects that are too far off, or too small.
The Imperfections of Distance are remedied in a great Measure by Telescopes; whose chief Use, that comes under our Consideration, is to discern the Stars, and other celestial Bodies.
To find out the first Inventor of these sorts of Glasses, it will be necessary to ​learn who first found out the Properties of Convex and Concave Glasses in the Refraction of Light. Dr. Plot has collected a great deal concerning F. Bacon, in his Natural History of Oxfordshire; which seems to put it out of doubt that he knew that great Objects might appear little, and small Objects appear great; that distant Objects would seem near, and near Objects seem afar off, by different Applications of Convex and Concave Glasses; upon the Credit of which Authorities, Mr. Molineux (n)(n) Dioptric. Pag. 256, 257, 258. attributes the Invention of Spectacles to this learned Friar, the Time to which their earliest Use may be traced, agreeing very well with the Time in which he lived; but how far F. Bacon went, we know not: So that we must go into Holland(o) Borellus de vero Inventore Telescopii, pag. 30. for the first Inventors of these excellent Instruments, and there they were first found out by one Zacharias Joannides (o), a Spectacle-maker (p) of Middleburgh in Zeland; in 1590(p) Ibid. Pag. 35. (q) he presented a Tellescope of Two Glasses to Prince Maurice,(q) Ibid. Pag. 30. and another to Arch-Duke Albert, the former of whom apprehending that they might be of great Use in War, desired him to conceal his Secret. For this Reason, his Name was so little known, that neither Des Cartes (r)(r) Dioptric. nor ​Gerhard Vossius (s) had ever heard any thing of him, when they attributed the Invention of Telescopes to Jacobus Metius of Alkmaer.(s) De scientiis Mathemat. p. 70. However it taking Air, Galileo Galilei took the Hint, and made several Telescopes, by which making Observations upon heavenly Bodies, he got himself immortal Honour. Thereby (t)(t) Vide Galilæi Nuntium sidereum primò ni fallor, impressum, A.D. MDCVIII. he discovered Four Planets moving constantly round Jupiter, from thence usually called his Satellits, which afterwards were observed to have a constant, regular, and periodical Motion. This Motion is now so exactly known, that Mr. Flamstead, who is one of the most accurate Observers that ever was, has been able to calculate Tables of the Eclipses of the several Satellits, according to which, Astronomers in different quarters of the World, having Notice of the precise Time when to look for them, have found them to answer to his Predictions, and published their Observations accordingly. This is an effectual Answer to all that Rhapsody which Stubbe (u)(u) Plus Ultra reduced to a Non plus. Pag. 28, 36. has collected in his Brutal Answer to Mr. Glanvile's Plus Ultra, about the Uncertainty of all Observations made by Telescopes; since it is impossible to calculate the Duration of any Motion justly by fallacious and uncertain Methods. By the Eclipses of ​Jupiter's Satellits, Longitudes would soon be exactly determined if Tubes of any Length could be managed at Sea. (w)(w) Vide Philosoph. Transact. n. 177. But Jupiter is not the only Planet about which things anciently unknown have been revealed by this noble Instrument. The Moon has been discovered to be an Earth endued with a libratory Motion, of an uneven Surface, which has something analogous to Hills and Dales, Plains and Seas; and a new Geography (if one may use that Word without a Blunder) with accurate Maps has been published by the great Hevelius (x),(x) Selenograph. and improved by Ricciolus (y), by which Eclipses may be observed much more nicely than could be done formerly.(y) Almagest. The Sun has been found to have Spots at some times; the Planets to move round their Axes; Saturn to have a Luminous Ring round about his Body, which in some Positions appears like two Handles, as they are commonly called, or large Prominencies on opposite Parts of his Limb, carried along with him, beside Five Planets moving periodically about him, as those others do about Jupiter: The milky Way to be a Cluster of numberless Stars; the other parts of the Heaven to be filled with an incredible Number of fixed Stars, of which, if Hevelius's Globes are ever ​published, the World may hope to see a Catalogue. These are some of the remarkable Discoveries that have been made by Telescopes: And as new Things have been revealed, so old ones have been much more nicely observed, than formerly it was possible to observe them.
But I need not enlarge upon particular Proofs of that, which every Astronomical Book, printed within these Fifty Years, is full of. If I should, it would be said, perhaps, that I had only copied from the French Author of the Plurality of Worlds, so often mentioned already.
As some Things are too far off, so others are too small to be seen without help. This last Defect is admirably supplied by Microscopes, invented by the same Zacharias Joannides (z);(z) Borellus, ubi supra, p. 35. which, besides Miscellaneous and Occasional Observations, have been applied to Anatomy, by Malpighius, Leeuwenhoeck, Grew, Havers, and several others. The first very considerable Essay to shew what might be discovered in Nature, by the help of Microscopes, was made by Dr. Hook, in his Micrography; wherein he made various Observations, upon very different Sorts of Bodies. One may easily imagine what Light they must needs give unto the nicer Mechanism of most Kinds of Bodies, ​when Monsieur Leeuwenhoeck has plainly proved, that he could, with his Glasses, discern Bodies several Millions of Times less than a Grain of Sand. This may be relied upon, because Dr. Hook, who examined what Leeuwenhoeck says of the little Animals which he discerned in Water, of which he tells the most wonderful Things, does, in his Microscopium, attest the Truth of Leeuwenhoeck's Observations.
Besides these which are of more universal Use, several other Instruments have been invented, which have been very serviceable to find out the Properties of Natural Bodies; and by which several Things of very great Moment, utterly unknown to the Ancients, have been detected. As,
(a) Borellus de motu Animalium Part. II. Prop. clxxv.1. The Thermometer, invented (a) by Sanctorius, an eminent Physician of Padua. Its immediate Use is, to determine the several Degrees of Heat and Cold; of which our Senses can give us but uncertain Notices; because they do not so much inform us of the State of the Air in it self, as what its Operations are at that Time upon our Bodies. But Sanctorius used only open Vessels, which are of small Use, since Liquors may rise or fall in the Tubes, as well from the Increase or ​Diminution of the Weight of the Air, as of Heat and Cold. That Defect was remedied by Mr. Boyle (b),(b) See his Thermometrical Thoughts, prefixed to his History of Cold. who sealed up the Liquors in the Tubes, Hermetically, that so nothing but only Heat and Cold might have any Operation upon them. The Uses to which they have been applied, may be seen at large in Mr. Boyle's History of Cold, and the Experiments of the Academy del Cimento.
2. The Baroscope, or Torricellian Experiment; so called from its Inventor, Evangelista Torricelli, a Florentine Mathematician; who, about the Year 1643. found that Quick-Silver would stand erect in a Tube, above 28 Inches from the Surface of other Quick-Silver into which the Tube was immersed, if it was before well purged of Air. This noble Experiment soon convinced the World, that the Air is an actually heavy Body, and gravitates upon every Thing here below. This Gravitation being found unequal at several Times, Mr. Boyle applied this Instrument to Mechanical Uses (c),(c) Philosof. Transact. Num. 9, 10, 11-55. and shewed how it might teach us to know the Differences and Changes of Weather; when dry, and when wet; since, by a vast Number of Observations, he had learnt, that in dry Weather the Air drove up the Mercury, and in wet ​Weather let it fall again; though never lower than 28 Inches, and scarce ever higher than 32.
3. These Observations, with other Collateral Experiments, induced him to believe that the Air was, in Truth, a Springy Body, which expanded or contracted it self in a Reciprocal Proportion, to the Increase or Lessening of the Compression of the Ambient Bodies. For which he invented an Instrument to draw the Air out of Vessels that were filled with it, by Suction. The first Essays of that kind seem to have been made some Years before his appeared, by Otto Guerick of Magdebourg; but as he applied them chiefly to the Gravitation of the Air, without taking any notice of its Spring; so they were very imperfect, when compared to Mr. Boyle's. By this Air-Pump, as it is usually called, he discovered Abundance of Properties in the Air, before never suspected to be in it. What they are, either considered singly, or in their Operations upon all sorts of Bodies, may be seen at large in his Physico-Mechanical Experiments concerning the Weight and Spring of the Air; and in several of his other Discourses upon the same Argument; some of which are printed by themselves, and others in the ​Philosophical Transactions (d).(d) Num. 62, 63, 122. Vide Catalogue of Mr. Boyle's Works, at the End of the First Part of the Medicinal Experiments, Printed 1692. in Twelves. How far they may be relied upon appears from this; That though Hobbes and Linus have taken a great deal of Pains to destroy Mr. Boyle's Theory, yet they have had few or no Abettors: Whereas the Doctrine of the Weight and Spring of the Air, first made thorowly intelligible by Mr. Boyle, has universally gained Assent from Philosophers of all Nations who have, for these last Thirty Years, busied themselves about Natural Enquiries.
4. The Invention of Pendulum-Clocks ought here to be remembred, since from them it appears, that the Diurnal Motion of the Earth is not so exactly Periodical, as that a true Equation of Time can thereby be obtained; but by this Instrument, the Measure of the Variation being once adjusted, the true Time of the Earth's Diurnal Motion can, at all Seasons of the Year, be more exactly known. The Use of it in making of Astronomical Observations is also very obvious; for they could not anciently be so minute as they are at present, for want of such nice Sub-Divisions of an equable Motion as it affords. The Invention of this noble Instrument is attributed, by the Publisher of ​the Experiments of the Academy del Cimento, to Galileo Galilei, who found out so many excellent Theorems of the Nature and Proportions of the Motions of Projected and Vibrating Bodies. He says that Galileo first applied the Pendulum to Clock-work; and that his Son Vincenzio put it in practice in the Year 1649 (e).(c) Experiments of the Academy del Cimento, p. 12. Edit. Eng. It was little taken notice of, however, in these Parts, till Monsieur Huygens revived or invented it a-new; to whom, for that Reason, the Glory of finding out this useful Instrument is commonly attributed. Upon this Occasion I ought not to omit that great Improvement of Watches, by adding a Second Spring to balance the First; (as the Pendulum in a Clock does the Weights) which also is attributed to Monsieur Huygens, though he and Dr. Hook have both contended for the Honour of this useful Invention. It appears by the Philosophical Transactions, and by Dr. Hook's Lectures, that he had a right Notion of this Matter, and that he had made several Essays to reduce it to Practice, some Years before any of Monsieur Huygens's Watches were produced; but that Monsieur Huygens first made Pendulum-Watches (so they are commonly called) that proved thoroughly serviceable. These will not be disputed to ​be Modern Inventions, since the whole Business of Clocks and Watches was unknown to all, even the Arabian, Antiquity (f):(f) See Dr. Edw. Bernard's Letter to Dr. Huntingdon, about the Latitude of Twenty Fixed Stars, from Arabian Observat. Phil. Trans. Their Astronomers measured their Time by Hour-Glasses of Water, or Vibrating Strings of several Lengths; which would, indeed, serve them, in most Cases, to measure Time nicely by, whilst they were observing; though they were of no Use upon other Occasions; and even then were liable to great Hazards.
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