48 
REPORT —1S54. 
new field to science. In the first place, that the cylindrical principle, in general, is 
superior to the spherical, will appear from the circumstance,that a perfectlvcvlindiical 
lens is free from the defects of spherical aberration, and that the opposite rectangular 
planes combine in forming ellipses in their intersections, and consequently show a 
greater precision, distinctness and luminousness, and less contraction of dimeniiona; 
they therefore admit of enlarged visual angles. The cylindrical system, moreovif, 
renders it practicable to form curves of all kinds, for instance, paraboles, hyperboles, 
ellipses, &c., which is impracticable in the spherical system. In the second plan-, 
tbe aforementioned machine is so constructed that every lens, even for spectacle, 
«PPfY s i centrcd > s * n ce the cross lines of the two planes pass through the middle, 
whilst the centralization of spherical object-lenses is, as known, very difficult ami 
imperfect. This defect arises both in the best spherical and cylindrical lenses from 
their being hitherto ground by hand; tile im perfection becoming more evident In 
the latter than the grossest defects in the former ; and this doubtless is the icasim 
why science has not bestowed more attention ou cylindrical lenses. No one would 
expect the formation ol a perfectly circular cone without tbe instrumentality of a 
turning lathe ; and, in like manner, what the turning lathe is to this or other artklrt 
to be finely rounded, the machine I wish to introduce is for optical lenses; hence, tw, 
the advantage of the perfectness of its productions, and also the rapidity of tbe 
manufacturing process. In the third place, in order to prove the better preservation 
of the eyes by the use of cylindrical lenses than by the spherical, it is only neasnary 
to observe that two cylindrical planes, intersecting each other at right angle*, h»"j 
the effect of neutralizing the defect of spherical aberration ; whilst two parol ' 
spherical planes produce the effect of doubling the imperfection: moreover, wewvd 
uly to advert to the structure of the eye in man and other animals, which « not 
spherical, nor achromatic, and is nevertheless free from the defect of aberration:-'! 
Snnrr. ; m c J l,ptic 8hape * which hl creation appears to predominate, as for «• 
SSil i the planeta yy orbits, in magnetic currents. &c. And, since the effect of • 
eve Hlinw B enS *^f roac ies tbut °f an ellipse, and since, moreover, an optically disca* 
that fl rTrf f 8t, f B [H Qte / de P a rtme from the spherical form, it is equally apparej 1 
tnkl ,,l! 5 e Cy, ' IU riC Iens w the best adapted as the passage of the rays not on 
; , c in ab otrt the centre, but on evc-y point of the surface, thus effecting 
quab,e and perfectly regular distribution of light on all points. 
On Natural Occurrences that impair the Vision of good Telescopes. 
By Cornelius Varlee. 
res!iu isTr*™ C T rk r Ulat pver ything moving on the earth causes vibrations : 
the verv h«. • k°* * 0t J ^ ne be known till high magnifying proven their exis ^ 
2lacSi«t br r° J Sta,,ds C0im 7 them to the telescope. He stated a 
wSabom?T '% * he V™* on Bromley Common, he heard, 
mSIf off. thrir dSr S2*• second, a one-horse cart; third, a stage coach 
met in revere dl8tanc<?9 n,ld approach were indicated. '1 hesehe b 
Which wauf^A- !r ? m tlleir differi »B speed. This proved tremor- 
inferred the earth' powers* ftnd from the number of greater causes h j 
means of insnllo BUrf8CC t0 be rarely o. never free from such. He 
rubber under thrm ? S .° as lJ tu nvoid tbcm : —First, cushions of wool or | |jf!l 
has been done r v** - ® econd » supporting the telescope by pulley 1 nlJ j tL . in¬ 
capable of rerpiuT ^ cwtQ1,ians **4 success), such blocks and ropes beiogA ^. p 
mSst perfect tr T“ ittin « ^ratioi or tremors, and 
from tK SSl and fh r h, 8 h “orthern support of polar axes 
might be made real rlk^ S ? a P ward «» hut heavy top bars leaning 6^.^ tie 
sea roaring all crniwSSS ° r . daD, P e »‘ s - Sounds of all sorts, percussion-, gUD( j, 
and impair their npcf lbratl0ns that act on the materials of both teleecnp 
Thi 3 tiling affect, al, aSSjRS e“S '%£**»* 
