TELESCOPE, HISTORY OF THE. It has been the fate of almost every instrument by which science has been extended, or the well-being of man promoted, that the precise epoch of its invention, and even the name of the individual to whom the world is indebted for it, are alike unknown. This is particularly the case with the telescope, of which the earliest notices are that it existed in England and in Hollana near the end of the 16th or in the beginning of the 17th century.
There is in Strabo a passage p. 180, Falconer's ed. ; p. 138, g Carsaub.') in which, speaking of the enlargement of the sun's disc at his rising and setting in the sea, it is stated that the rays (of light) in passing through the vapours which rise from the water, as through tubes, are dilated, and thus cause the apparent to be greater than the real magnitude (of the object); and from this it has been inferred (Dutens, Recherches,' &c.), though the inference is probably without foundation, that there then existed tubes furnished with lenses for magnifying objects by refracting the light. It would be needless to make any observations on an inference founded upon an hypothesis so obscurely expressed : the words in Strabo probably signify only that the rays of light might become divergent in passing along the intervals between the particles of vapour.
Omitting then all notice of this, and of the ill-understood passages in Aristophanes (' Clouds ') and Pliny (lib. xxxvi., c. 67) concerning transparent spheres, or lenses for concentrating the rays of light, it must be acknowledged that before the end of the 19th century lenses of glare were in constant use for the purpose of assisting the eye in obtaining distinctness. of vision. Vitello, a uative of Poland, in that century, gave some obscure indications of the apparent magnitudes of objects when viewed through a segment of a sphere of glass; and Roger Bacon, in his ' Opus Majus,' both mentions the like fact, and expreeses himself In such a manner as to Indicate that in his time the died In 1292) spectacles were already in use. Ile may not have actually made combinations of lenses In one instrument, but there is no doubt of his being aware of the fact that lenses might be arranged o that objects seen through them would appear to be magnified.
The idea being known to the learned, it is scarcely possible to doubt that the combluation of two lenses, or of a concave or convex mirror and a lens, must have been often made during the three centuries which elapsed between the time of Bacon and that which is generally cousidered as the epoch of the invention of telescopes. Dr. Dee, in his preface to Euclid's ' Elements,' (1570) having mentioned that some skill is required to ascertain the numerical strength of an enemy's( force when at a distance, observes that the " captain, or whosoever is careful to come near the truth herein, besides the judg ment of his eye, the help of his geometrical instrument, ring, or staff° astronomical (probably for determining the measure of distances] may wonderfully help himself by perspectire glasses." These Lest can only signify some kind of telescope, which therefore must have been then in general use. And in the Pantomotria' of 1)igges (1571) it it stated that " by concave and convex mirrors of circular (spherical) and parabolic forms, or by frames of them placed at due angles, and using the aid of transparent glasses which may break, or unite, the images produced by the reflections of the mirrors, there may he represented a whole region : also any part of it may be augmented, so that a small object may be discerned as plainly as if It were close to the observer, though it may be as far distant as the eye can descries" In the pre face to the second edition (1591) the editor, who was the author's son, affirms that "by proportional mirrors placed at convenient angles, his father could discover things far off, that be could know a man at the distance of three miles, and could read the superscriptions on coins deposited in the open fields." There is probably some exaggeration
in this account, but it is sufficiently manifest from it that reflecting telescopes, or optical instruments containing combinations of mirrors and lenses, were known in England before the end of the 16th century. The claim of Baptista Porta (between 1545 and 1615) to the invention of the telescope appears to have no other foundation than the circum stance 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 Borehlus, in his work entitled' De rem Telescopii Inventors; which was published in 1655 at the Hague, has given testimonials in favour of two persona; the first of these is Zechariah Jens, or Jansen, and the other, Hans Lapprcy, or Lippersheim, both of whom arc said to have been opticians, or spectacle.makers, residing at 3lidd1eburgh. In a letter written by a son of Jane, it is stated that the epoch of the discovery is the year 1590; but by another account, the year 1610. The same author has also given a letter from M. William Bored (envoy from the States of Holland to the Brittah Court) which seems to throw some light on the facts. The writer of the letter asserts that he was acquainted with the younger Zechariah Jana, when both of them were children, and had often hoard that the elder was the inventor of the microscope : he add, that, about the year 1610, the two opticians Jams and Lapprey first constructed telescopes, and that they presented one to Prince Maurice of Naimu, who desired that the invention might be kept secret as (the United Provinces being then at war with France) ho expected to obtain in the field, by means of the instrument, some advantages over the enemy. The writer further states that the invention be cause known, and that soon afterwards Adrian Isletlua and Cornelius Drebbel went to Middleburgh and purchased telescopes at the house of Jane This account differs from that which is given by Descartes, (' Dioptrics, cap. 1) who, writing in Holland, states that about thirty years previously, Metiva (who wan, he observes, a native of Alckmaer), haring always taken pleasure in forming burning mirrors and lenses of glare and of ice, by chance placed at the extremities of a tube two lenses, one thicker in the middle, and the other thinner, than about the edge (convex and concave); and thus, he adds, was formed the instrument which is called a telescope. The ' Dioptriee was published at Leyden, in 1637, and therefore the time of the supposed Invention by 3letius in nearly coincident with that at which, according to Borate, it was made by Jana. From the papers of Harriot, it appears that this mathematician observed spots on the sun, in 1610, with telescopes simplifying from ten to thirty times; but It is uncertain whether he got them from Holland, or whether they were made in this country; and the only conclusions at which It is possible now to arrive, are, that telescopes were known In England and Holland about the end of the 16th century, and that in both countries they were then in a form which rendered them prac tically useful.