134 SUMMARY OF CURRENT RESEARCHES RELATING TO 



by the homogeneous-immersion method, both in theory and in practice, to 

 the problem of correcting an objective of moderate air angle. 



On this principle, by which the Amici type of construction is 

 brought to its full eJBficiency, is based the optical advantage of the 

 homogeneous-immersion method : i.e. the advance of defining power 

 per se which is due to the exclusion of disproportionate aberration, and 

 the increase of aperture which is reconcilable with perfect definition 

 without needing any reduction of working distance apart from the 

 requirements of technical work in high-power systems." 



'The Northern Microscopist.' * — We are pleased to see the first 

 number of a new Microscopical Journal under this title, edited by 

 Mr. George E. Davis, a Fellow of the Society, It is hoped that its 

 establishment " will be a bond of union between workers in the North, 

 and that it will bring to the fore many men whose researches have 

 scarcely been heard of, on account of their distance from the great 

 microscopical centres ; " and amongst its aims is the keeping of a 

 record of the proceedings of the chief Microscopical Societies in the 

 North, and so furnishing each individual member with at least as 

 much permanent information as he would obtain if the Society to 

 which he belonged published its own transactions — possibly more. 



/3. Collecting, Mounting, and Examining Objects. 



Dr. Maddox's modified Aeroconiscope. — The modified form of 

 Dr. Maddox's " Aeroconiscope," exhibited by him at the ordinary 

 meeting of the Society on the 10th November, is figured in the 

 accompanying woodcut.| It can be used as a vane, like the one 

 employed in the experiments recorded in the ' Monthly Microscopical 

 Journal ' for 1870 (where the original form is figured), or with an 

 aspirator, which can be driven by any means selected to draw a current 

 of air through the instrument. 



It consists essentially of an apparatus to collect the atmospheric 

 dust, &c., and deliver it upon a slightly glutinous surface. In this 

 case a glass tube b, and a funnel a, which supports a platinum wire 

 bent as shown in the figure, to hold a thin microscope cover-glass, and 

 at the opposite end to the funnel a pair of wings, attached to a split 

 ring, which slides on 6, the whole supported, as seen in Fig. 22, on a 

 conically pointed steel pin. This pin can be screwed into a reversible 

 clamping screw, to fix on the edge of a table, chair, or window-ledge, 

 or slips into a socket on the side of the upper vessel of the aspirator, as 

 at d. The glass tube of the vane, if used fixed, is attached by a short 

 piece of indiarubber tubing, by which the air, after depositing the dust, 

 escapes into the upper vessel previously filled with water, and allowed 

 to empty itself into the lower vessel,' thus creating a slight current 

 through the apparatus. If used as a vane for the wind to blow 

 through, of course it would be necessary to detach the indiarubber 

 tubing, and allow the vane to gyrate upon the conical pin, fixed, if 



* ' The Northern Microscopist,' vol. i. No. 1. January. 24 pp. 1 plate and 

 2 figs. (8vo. London and Manchester, 1881.) Gd. 

 t See 'British Medical Journal,' Nov. 20, 1880. 



