The second difficulty to which we have referred, namely, the expense of endowment, scarcely merits our consideration. A very large sum is annually expended by the State in support of the existing societies, and a considerable number of those who would be members of the General Institute, already enjoy the liberality of Government. But, independently of these considerations, the organization of a National Institute would be a measure of real and direct economy. The inquiries connected with the arts, whether useful or ornamental, which are required by the Government, have hitherto been carried on by Committees of Parliament; and had we a return of all the sums annually spent in scientific inquiries, and for scientific purposes, the amount would be found to exceed greatly that of the annual expense, however liberal, of a National Institution. Every question connected with ship-building, with our steam navy, our light-houses, our harbours, our railways, our mines, our fisheries, our sanatory establishments, our agriculture, our statistics, our fine and useful arts, would be investigated and reported upon by a Committee of Academicians; and while the money of the State would thus be saved, the national resources would be augmented, and all the material interests of the country, under the combined energies of her Art and her Science, would advance with a firm and accelerated step.

But there are grounds higher than utilitarian, on which we would plead the national endowment of science and literature. In ancient times, when knowledge had a limited range, and was but slightly connected with the wants of life, the sage stood even on a higher level than the hero and the lawgiver, and History has preserved his name in her imperishable record, when theirs has disap

peared from its page. Archimedes lives in the memory of thousands who have forgotten the tyrants of Syracuse, and the Roman consul who subdued it. The halo which encircled Galileo under the tortures of the Inquisition, extinguishes in its blaze even the names of his tormentors; and Newton's glory will throw a lustre over the name of England, when time has paled the light reflected from her warriors. The renown of military achievements appeals but to the country which they benefit and adorn : It lives but in the obelisk of granite: It illuminates but the vernacular page. Subjugated nations turn from the proud monument that degrades them, and the vanquished warrior spurns the record of his humiliation or his shame. Even the patriot traveller makes a deduction from military glory, when he surveys the red track of desolation and of war, and the tears which the widow and the orphan shed corrode the inscription that is written in blood. How different are our associations with the tablet of marble, or the monument of bronze, which emblazon the deeds of the sage and the philanthropist! Their paler lustre irradiates a wider sphere, and excites a warmer sympathy. No trophies of war are hung in the temple which they adorn, and no assailing foe desecrates its shrine. In the anthem from its choir the cry of human suffering never mingles, and in the procession of the intellectual victor, ignorance and crime are alone bound to his car. The achievements of genius, could the wings of light convey them, would be prized in the other worlds of our system,—in the other systems of the universe. They are the bequests which man offers to his race, a gift to universal humanity at first to civilisation-at last to barbarism.

Views like these must have influenced the mind of

Newton, when, in an elaborate document which he left in duplicate behind him, he recommended the systematic endowment of Science. Were the British Parliament to try this question at its bar, and summon as witnesses the wisest of their race, what name, or what constellation of names, could countervail against the High Priest of Science, when he proposes to rebuild its Temple upon a broader basis, and give its arches a wider span, and its domes a loftier elevation!

CHAPTER V.

MISTAKE OF NEWTON IN SUPPOSING THE LENGTH OF THE SPECTRA TO BE THE SAME IN ALL BODIES-AND IN DESPAIRING OF THE IMPROVEMENT OF REFRACTING TELESCOPES-IN HIS CONTROVERSY WITH LUCAS HE WAS ON THE EVE OF DISCOVERING THE DIFFERENT DISPERSIVE POWERS OF BODIES-MR. CHESTER MORE HALL MAKES THIS DISCOVERY, AND CONSTRUCTS ACHROMATIC TELESCOPES, BUT DOES NOT PUBLISH HIS DISCOVERY-MR. DOLLOND REDISCOVERS THE PRINCIPLE OF THE ACHROMATIC TELESCOPE, AND TAKES OUT A PATENT—PRINCIPLE OF THE ACHROMATIC TELESCOPE EXPLAINED-DR. BLAIR'S APLANATIC TELESCOPE-GREAT IMPROVEMENT ON THE ACHROMATIC TELESCOPE BY THE FLINT GLASS OF GUINANT, FRAUNHOFER, AND BONTEMPS MISTAKE OF NEWTON IN FORMING HIS SPECTRUM FROM THE SUN'S DISC-DARK LINES IN THE SPECTRUM-NEWTON'S ANALYSIS OF THE SPECTRUM INCORRECT-NEW ANALYSIS OF THE SPECTRUM BY ABSORPTION, ETC., DEFENDED AGAINST THE OBJECTIONS OF HELMHOLTZ, BERNARD, AND OTHERS-CHANGE IN THE REFRANGIBILITY OF LIGHT MAINTAINED BY PROFESSOR STOKER-OBJECTIONS TO HIS THEORY.

THE two great doctrines of the different refrangibility of the rays of light, and of the composition of white light, by mixing all the rays of the spectrum, having been established by Newton on an impregnable basis, we come now to describe some of the other results which he obtained regarding the prismatic spectrum and its colours, to point out the errors which he committed, to shew the influence which they had on the progress of optics, and to give an account of the remarkable discoveries which have been made in this branch of science during the last and the present century.

There are few facts in the history of optics more sin

gular than that Newton should have believed that all bodies when shaped into prisms produced prismatic spectra of equal length, or separated, or dispersed the red and violet rays to equal distances, when the mean refraction, or the refraction of the middle ray of the spectrum was the same. This opinion, which he deduced from no direct experiments, and into which no theoretical views could have led him, seems to have been impressed on his mind with all the force of an axiom. In one of his experiments he had occasion to counteract the refraction of a prism of glass by a prism of water; and had he completed the experiment, and studied the result of it when the mean refraction of the two prisms was the same, he could not have failed to observe that the prism of water did not correct the colour of the prism of glass, and would have thus been led to one of the most important truths in optics, that different bodies have different dispersive powers, or produce prismatic spectra of different lengths, when their mean refraction is the same. It is curious to observe, as happened in this experiment, what trifling circumstances often arrest the philosopher when on the very verge of a discovery. Newton had mixed with the water which he used in his prism a little sugar of lead, in order to increase the refractive power of the water; but the sugar of lead having a higher dispersive power than water, made the dispersive power of the water prism equal to that of the prism of glass; so that if Newton had completed the experiment, the use of the sugar of lead would have prevented him from making an important discovery, which was almost in his possession. Had he, on the contrary, increased the angle of his water prism till it produced the same deviation of the mean ray of the