NATURAL HISTORY MISCELLANY. 187 
of the falsity of our high powers (1-8th to 1-16th) has led Dr. 
Royston Pigott to pay more attention to the lower powers, and he 
finds that though you may not get so much actual amplification, 
you yet get a truer effect, and greater clearness of detail, by 
employing very carefully made low powers (1-2d to 1-5th), and 
increasing the magnifying power at the other end of the micro- 
scope, 7. e., the eye-piece. We have in this way seen the beaded 
structure of the scales of the Podura more satisfactorily than with 
very high objectives, even’ when corrected so far as they would 
admit, and we may say the same of some Diatom-valves, e. g., Pl. 
formosum. It would be most important to know how far such a 
change of combination would be useful in histological work. 
The general upshot of Dr. Royston Pigott’s investigations ap- 
pears to be that it is desirable to shift the burden, hitherto cast 
almost wholly upon the objective, to the other parts of the instru- 
ment. We should be content with an objective as high as a fifth, 
or even less. A very deep eye-piece is to be used; and to correct 
residuary aberrations of the objective, and at the same time ampli- 
fy, Dr. Pigott has introduced an important adjustable combination 
between the eye-piece and the object-glass. There seems to be consid- 
erable reason for the step proposed by Dr. Royston Pigott. Just 
as great results were obtained in passing from the single lens or 
combination to the compound microscope of eye-piece and objec- 
tive, so by adding distinct integral factors to these two, such as 
Dr. Pigott’s “ aplanatic searcher,” we may obtain excellences quite 
impossible by any amount of attention bestowed on the objective 
alone, or only with difficulty reached by long labour, leading to 
very high price for high powers. 
Dr. Pigott has, during the past year, published some account of 
his researches in the Quarterly Journal of Microscopical Science, 
» and has communicated papers to the Royal Society, one of which 
is about to appear in the Philosophical Transactions 
Naturally, at first, the makers in London and the Mascieveien! 
Society were sorely tried by Dr. Pigott’s exposure of the Podura- 
scale, but we hear, as one good result already obtained, that 
Messrs. Powell and Lealand have constructed a new 1-8th, both 
dry and immersion, with great care, which is declared to be the 
best glass yet made. It has been proposed to form a committee 
for the purpose of examining carefully as to penetration, defini- 
tion, and angular aperture, the best glasses of our English makers, 
