278 Transactions of the [irHL^.ttWa' 



for their convenience to give an abstract of the specification of Mr. 

 Samuel Hohnes, of 12, Bmnswick Terrace, Lower Road, Eotherhithe, 

 who has recently secured his improvements in the instrument by a 

 patent. In the full description of the illustrations published in the 

 specification, the patentee observes : — 



" My invention consists in the use of two object-glasses or portions 

 of two object-glasses, or of one object-glass divided into two parts, to 

 supply through two eye-pieces a binocular and stereoscopic view of 

 opaque or transparent microscopic objects while illuminated by reflected 

 or transmitted light, and also in the use of certain mechanical means 

 herein described, or their equivalents, for securing the motion in re- 

 quired dii'ections, or rest in necessary positions of the optical parts of 

 such combinations for obtaining monocular or binocular vision. 



" The Objective. — I take an ordinary object-piece, and by a circular 

 saw divide it along its line of collimation, and afterwards rejoin the 

 halves by screws and steady pins, until as an objective it is in as per- 

 fect a state of adjustment as before division. It is then capable of 

 acting as an objective for one or two eyes, according to the position 

 assumed by the two halves under the control of the mechanical part of 

 the instrument when the direct light is stopped out. 



" According to another method, I work the lenses of an achromatic 

 object-piece out of divided and rejoined discs of glass, which when 

 finished and fixed in a divided mounting temj)orarily held together for 

 that purpose may be afterwards sejiarated by dissolving out the cement 

 by which the halves of the discs were originally conjoined. 



" Or lastly, I make two whole object-glasses, and fix one into each 

 half of a divided mount, cutting away only such portion as will allow 

 of proper approximation. This method is available for high powers 

 and for binocular use only. 



" In all cases I cut the usual screw-thread on the objectives to affix 

 them to the body, and more surely secure their halves in their respec- 

 tive places in the divided body-tube of the instrument by two small 

 milled-headed screws. 



" The Stand. — Figs. 1, 2, and 3, represent a front, side, and back view 

 respectively of the mechanical arrangement of a microscope according 

 to my invention, and Fig. 4 shows a section of its optical arrangements. 



" A reference to these drawings will show that two rules or bars 

 are jointed at one end (like a sector), and this joint is in the plane of 

 focus of the object-glass. The upper ends of the bars are free to 

 separate a distance equal to the width of the two eyes (about 2* inches), 

 when operated by the upper millhead and its levers, as shown. On 

 these two bars slide respectively the two halves of the bisected tube 

 carrying the object-glass and eye-piece or eye-pieces, according as to 

 whether the body-tube is closed for observing with one eye or sepa- 

 rated for binocular use. This sliding motion is given by a crank on 

 the lower millhead, and serves to make the focus of the object-glass 

 coincide with the centre of motion of the two bars. The central mill- 

 head gives a separate motion of small extent to each of the half body 

 tubes, when any little inequality of focal length, either of the eyes of 

 the observer or in the glasses, might make one of the two images 



