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while it was being fused in the pot. However this may have been, he succeeded in making disks of larger and larger size.

To utilize these disks required an optician of corresponding skill to grind and polish them into proper shape. Such an artist was found in the person of Fraunhofer, of Munich, who, about 1820, made telescopes as large as nine inches aperture. He did not stop here, but, about 1840, succeeded in making two objectives, each of fourteen German inches, or about fifteen English inches in diameter. These, far exceeding any before made, were at the time regarded as marvellous. One of these instruments was acquired by the Pulkova Observatory in Russia; the other was acquired by the Harvard Observatory at Cambridge, Mass. The latter, after a lapse of more than half a century, is still in efficient use.

After Fraunhofer's death it was doubtful whether his skill had died with him, or had passed to a successor. The latter appeared where none would have thought of looking for him, in the person of an obscure portrait painter of Cambridgeport, Mass., named Alvan Clark. The fact that such a man, with scarcely the elements of technical education and without training in the use of optical instruments, should have done what he did, illustrates in a striking way what an important element native talent is in such a case. He seemed to have an intuitive conception of the nature of the problem, coupled with extraordinary acuteness of vision in solving