Telescopes—Life of Fraunhofer. 307 
1805, M. Utzschneider constructed furnaces for carrying 
on the experiments upon a well organized plan. The first 
attempt created much expense, on account of the repeat- 
ed experiments which it required, but it nevertheless fur- 
nished several good pieces of both kinds of glass 
optician, Riggl, polished the first lenses in 1806 and 1807, 
At this period Fraunhofer found himself in a very critical 
situation. Professor Schiegg always encouraged him to go 
to M. Utzschneider, but Fraunhofer was long in resolving to 
do this, believing that the latter had forgotten him, and 
knowing that he was well satisfied with his own optician. 
M. Utzschneider received Fraunhofer in a very friendly 
instruments of the observatory of Buda. It was afterwards 
agreed to transfer all the optical part of the establishment 
to Benedictbauern, and to give the complete direction of it 
to Fraunhofer. Our philosopher had already studied catop- 
trics, and had even written a Memoir on the aberration 
which takes place without the axis in reflecting telescopes. 
He showed that hyperbolic mirrors are preferable to para- 
bolic ones, and he also communicated the invention of a 
machine for polishing piperbone surfaces. He now, howev- 
er, resolved to give up this branch of the subject, as his time 
also the advantage of making the result independent of the 
skill of the workman. 
n examining the glass which he used in reference to the 
undulations and striz which it contains, he found that, in 
the flint glass manufactured at Benedictbauern, there was 
