<P> Dollond did not reply to this, but soon afterwards he received an abstract of a paper by the Swedish mathematician and astronomer, Samuel Klingenstierna, which led him to doubt the accuracy of the results deduced by Newton on the dispersion of refracted light . Klingenstierna showed from purely geometrical considerations (fully appreciated by Dollond) that the results of Newton's experiments could not be brought into harmony with other universally accepted facts of refraction . </P> <P> As a practical man, Dollond at once put his doubts to the test of experiment: he confirmed the conclusions of Klingenstierna, discovered a difference far beyond his hopes in the refractive qualities of different kinds of glass with respect to the divergence of colors, and was thus rapidly led to the construction of lenses in which first the chromatic aberration--and afterwards--the spherical aberration were corrected . </P> <P> Dollond was aware of the conditions necessary for the attainment of achromatism in refracting telescopes, but relied on the accuracy of experiments made by Newton . His writings show that with the exception of his bravado, he would have arrived sooner at a discovery for which his mind was fully prepared . Dollond's paper recounts the successive steps by which he arrived at his discovery independently of Hall's earlier invention--and the logical processes by which these steps were suggested to his mind . </P> <P> In 1765 Peter Dollond (son of John Dollond) introduced the triple objective, which consisted of a combination of two convex lenses of crown glass with a concave flint lens between them . He made many telescopes of this kind . </P>

Who is generally credited with inventing the telescope first