TELESCOPE, HISTORY OF THK. 



TELESCOPE, HISTORY OF T1IK. 



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Omitting then all notice of thU, and of the ill-understood passage* 

 in Arietophsrm* (' Cloud* ') and J'liny (lib. xxxvi., c. 67) concerning 

 tran.|rriit spheres, or lenses for concentrating the ray* of light, it 

 must be acknowledged that before the end of the 13th century lenses 

 of flats were in constant u*e for the purpose of assisting the eye in 

 obtaining dittinctnew of rWon. Vitello,* native of Poland, in that 

 century, gave some obscure indioationi of the apparent magnitude* 

 of object* when viewed through a segment of a iphere of glass; 

 and Roger Bacon, in hi* ' Opus Majus,' both mention* th like fact, 

 and expresses himself in men a manner a* to indicate that in hi* 

 time (he died in 1292) (peotaole* were already in use. He may not 

 hare actually made combination* of leuae* in one inttrument, but there 

 U no doubt of hi* being aware of the fact that lenses might be arranged 

 so that object* wen through them would appear te be magnified. 



The idea, being known to the learned, it i* actively possible to 

 doubt that the combination of two lenie*, or of a concave or convex 

 mirror and a len*, must hare been often made during the three 

 oenturie* which elapsed between the time of Bacon and that which i* 

 generally considered a* the epoch of the invention of telescopes. Dr. 

 Dee, in hi* preface to Euclid'* 'Element*,' (1670) having mentioned 

 that *ome skill is required to ascertain the numerical strength of 

 an enemy'* force when at a distance, obnrve* that the " captain, or 

 whoaoever i* careful to come near the truth herein, beside* the judg- 

 ment of hi* eye, the help of hU geometrical instrument, ring, or 

 ctaffe astronomical [probably for determining the meaiure of distances] 

 may wonderfully help himself by pertptelive giant*." These last can 

 only signify some kind of telescope, which therefore must have been 

 then in general use. And in the ' Pantometria' of Digges (1571) it it 

 stated that " by concave and convex mirrors of circular (spherical) and 

 parabolic forms, or by frame* of them placed at due angles, and using 

 the aid of transparent glasses which may break, ur unite, the images 

 produced by the reflections of the mirrors, there may be represented 

 a whole region : also any part of it may be augmented, so that a small 

 object may be discerned a* plainly as if it were close to the observer, 

 though it may be as far distant as the eye can descrie." In the pre- 

 face to the second edition (1591) the editor, who was the author's sou, 

 affirms that " by proportional mirrors placed at convenient angles, his 

 father could discover things far off, that he could know a man at the 

 distance of three miles, and could read the superscriptions on coins 

 deposit**! in the open fields. " There is probably some exaggeration 

 in thi* account, but it is sufficiently manifest from it that reflecting 

 teleacupes, or optical instruments containing combinations of mirrors 

 and lenses, were known in England before the end of the 16th century. 

 The chum of Baptiata Porta (between 1545 and 1615) to the invention 

 of the telescope appears to hare no other foundation than the circuui- 

 ctance that he perceived a small object to be magnified when viewed 

 through a convex lens. ' 



It is highly probable that the telescope had been invented long 

 before the value of such an instrument was duly appreciated ; and it 

 may have been owing to the very gradual discovery of its importance 

 that the name of the inventor sunk into oblivion : about the middle 

 of the 17th century, however, an effort was made to discover the 

 traces of the invention, and Peter Borellus, in his work entitled ' 1 ' 

 vero Telescopii Inventore,' which was published in 1655 at the 

 Hague, ha* given testimonials in favour of two jiersons ; the first of 

 these i* Zachariah Jam, or Jansen, and the other, Hans Lapprey, or 

 Lippersheim, both of whom are said to have been opticians, or 

 spectacle-makers, residing at Middleburgh. In a letter written by a 

 son of Jans, it is stated that the epoch of the discovery is the year 

 1690 ; but by another account, the year 1610. The same author has 

 also given a letter from M. William Boreel (envoy from the States of 

 Holland to the British Court) which seems to throw some light on the 

 facts. The writer of the letter asserts that he was acquainted with 

 the younger Xaohariah Jans, when both of them were children, and 

 had often heard that the elder was the inventor of the microscope : he 

 adds that, about the year 1610, the two opticians Jans and Lapprey first 

 constructed telescopes, and that they presented one to Prince Maurice 

 of Nassau, who desired that the invention might be kept secret as 

 (tile United Provinces being then at war with France) he expected 

 to obtain in the field, by mean* of the instrument, some advantages 

 ow the enemy. The writer further states that the invention be- 

 came known, and that soon afterwards Adrian Metius and Cornelius 

 Drsbbcl went to Hiddleburgh and purchased telescopes at the 

 house of Jan*. This account differ* from that which is given by 

 Deacartes, (' Dioptrics,' cap. 1) who, writing in Holland, states that 

 about thirty year, previously, Metius (who was, he observes, a native 

 of Aldunaer), having always taken pleasure in forming burning- 

 mirron and lenses of glass and of ice, by chance placed at the 

 extremities of a tubs two lenses, one thicker in the middle, and the 

 other thinner, than about the edge (convex and concave) ; and thus, 

 be adds, was formed the instrument which is called a telescope. The 

 rics' was published st Leyden, in 1037, and therefore the 

 time of the supposed invention by Metius i* nearly coincident with 

 that at which, according to Borellus, it was made by Jan*. 

 the paper* of Harriot, it appears that this mathematician observed 

 spots on the son, in 1610, with telescope* magnifying from ten to 

 tkirty times; but it is) uncertain whether be got them from H..!l..nd. 

 or whether they were made in this country ; and the only conclusions 



at which it is possible now to arrive, are, that telescopes were 1 



itiul and Holland about the rnd of tin- 10th rmtiirr, and that 

 in both countries they were then in a form which rendered them prac- 

 tically useful. 



The two Jansens, father and son, appear to have used their tele- 

 scopes in observing the heavens ; and the Utter is said to have 

 remarked four small stars near Jupiter : it has been concluded from 

 thence, that he was the first diacoverer of the satellites of that planet ; 

 l >ut though this may be, he probably did not continue his observations 

 long enough to enable him to determine their distances from it, or the 

 times of their revolution*. 



The use of the telescope, and, probably, even the knowledge of thu 

 fact that it had been invented, must have been for many yean con- 

 fined to the north of Europe ; for it appears that it was not till the 

 year 1609 that Galileo, who then happened to be at Venice, heard from 

 a Herman a rumour of the discovery which was said to have been made 

 in Holland. The Italian philosopher states, in the ' Sidereus Nuncius," 

 that he had then no knowledge of the nature of the instrument, and 

 that he requested a friend at Paris to send him some informal!' 

 eerning it On being informed, merely, that it was a tube containing 

 glass lenses, his acquaintance with the nature of the refraction of light 

 enabled him, it is said, to discover that one of the lenses must have 

 been convex and the other concave, and also to determine the distance 

 at which they should be placed from one another in order that the 

 objects seen through them might appear magnified and <i 

 Without however supposing that Galileo was here guided by th 

 oal considerations merely, it is easy to conceive that as lenses of di 

 forms were then in use for spectacles, he might have obtained from an 

 M].ii,-j,iu some which were of different degrees of convexity and con- 

 cavity ; and after a few trials he must have found such as would 

 constitute an instrument possessing magnifying power. 



The telescopes which he constructed consisted of one convex object- 

 glass and one concave eye-glass, which were placed at the exti. 

 of a leaden tube ; and the first of them magnified the heights and 

 breadths of objects three times only. Soon afterwards he made one 

 which magnified eight times ; and subsequently he succeeded in form- 

 ing a telescope with a magnifying power which caused objects to appear 

 about thirty times as great as they appear to the unassisted eye. 



The knowledge which man had acquired of the visible heavens 

 received many important accessions from the discoveries that < 

 was enabled to make by means of the telescope. Except the sun .md 

 moon, not one of the celestial bodies had hitherto been observed to 

 have any visible form or magnitude, and it was to the eye of reason 

 alone that those appeared to be anything but plane surfaces. The 

 fixed stars and the planets were alike known only as luminous and 

 ill-defined points ; but when seen through a telescope, the planets were 

 found to have certain magnitudes, and some of them to undergo varia- 

 tions of form ; while the fixed stars appeared unchanged, or only 

 divested of the radiance with which they seem to be surrounded when 

 seen by the naked eye ; and hence it became obvious that the former 

 must constitute a distinct group of bodies infinitely nearer the earth 

 than the others. The sun, from the spots observed on his surface, was 

 found to revolve on its axis, and consequently was ascertained to be 

 globular; and the light and dark spaces on the moim were distinctly 

 perceived to be mountains and valleys, nearly resembling those features 

 on the surface of the earth. Galileo relates, in the work above 

 tioued, that in the year 1610 he discovered the four satellites of Jupi- 

 ter, and observed that they revolved about that planet as our moon 

 revolves about the earth. Nearly at the same time he observed that 

 Saturn presented a remarkable appearance : at first he thought it was 

 accompanied by two smaller planets ; but on using a telescope of supe- 

 rior magnifying power, these were found to be portions of a vast anuu- 

 lus which surrounds Saturn without touching his surface ; and soon 

 afterwards he ascertained the fact that Venus exhibited phases similar 

 to those of the moon. 



The species of telescope which was used by Galileo continu. 

 several years unchanged ; yet it is extremely defective, on account of 

 the small extent of the field of view which it affords when its magni- 

 fying power is considerable ; and the Bataviau or Galilean telescope, as 

 it was called, is now chiefly used in the form of an opera-glass. It is 

 due to the memory of Kepler to state that he pointed out (in his 

 I >io]i tries ') the possibility of forming telescopes with two lenses, both 

 of which are convex ; but he did not reduce his ideas to practice by 

 the construction of such an instrument, and the honour of having been 

 the first to do so is to be attributed to the Jesuit Schemer, who, in his 

 ' Rosa Ursina ' (1650), gives a description of telescopes with one convex 

 eye-glass. He observes that they cause the images of objects to appear 

 in inverted positions ; and odds, that thirteen years previously he had 

 used such a telescope in the presence of the Archduke Maximilian. 



Telescopes with a single convex eye-glass have been since designated 

 nHrn<,,,,irnl. from the circumstance that they were log employed f,,,- 

 celestial obn 'lie greater , ir fiVlil "(' view having 



caused' aiding the inversion of the image, to supersede 



for that pur|K>m) the telescopes of Galileo. It ought to be remarked, 

 however, tlmt telcscoin eye-glasses, l.y whieh the object 



might bo Been in * it appears to the naked eye. 



described by Kepi. ' nietd by Schemer ; but as they caused 



the object to appear much distorted and coloured about the margin of 



