ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 141 



of a strong angle-piece, leaving space for the free movement of tlio radial 

 swinging tail-piece. The arrangement is a modification of the plan adopted 

 some time ago by Mr. Bulloch, to remedy the flexure so commonly found 

 in the Zentmayer mechanism, where the stage is carried by a conical 

 spindle passing through a sheath in the lower end of the stem, the swinging 

 tail-piece fitting by means of a collar outside the sheath. 



Bausch & Lomb Optical Co.'s Combined Inverted and Vertical Micro- 

 scopes ("Laboratory" and ''University" Microscopes). — The Inverted 

 Microscope, in the forms issued by M. Nachet, is well known to micro- 

 scopists. The Bausch & Lomb Optical Co. have now combined it with 

 the ordinary vertical form, the principle involved being, they believe, 

 entirely new. " There is no question that the fact that the inverted could 

 only be used as such, and that it was but incomplete at the best, has pre- 

 cluded its more general use, and we have no doubt that offering them as we 

 do now by combining two instruments in one, and supplying each with 

 such complete adjustments as modern requirements demand, they will be 

 found to fill a necessity in certain branches and prove a great convenience 

 in others. . . . This form of instrument is particularly adapted for 

 chemical investigations, for the reason that crystals may be studied as 

 they lie in their natural position in any depth of fluid, and the head is 

 sufficiently distant from the stage not to inhale any fumes. Further than 

 this, it is valuable in the examination of diatomacero and other objects in 

 water which are heavier than it, and therefore sink to the bottom ; also 

 in moist histological preparations, as they adhere to the surface of the 

 slide, and are therefore in one plane. It is also an excellent dissecting 

 Microscope, as it is partially erecting, offers no hindrance to manipu- 

 lation with any power, and makes it convenient to observe the object 

 directly." * 



There are two forms, the " Laboratory " and the " University." 



The " Laboratory " Microscope when used as an inverted instrument, 

 is shown in fig. 2. The mirror-bar swings on an axis in the plane of the 

 stage to any point above or below it. The mirror and substage are adjust- 

 able on the mirror-bar. The substage carries a revolving diaphragm, and 

 is fixed on a pivot so that it will swing in and out of the optic axis, 

 allowing the polarizer to be attached and ready for instant use. On the 

 slide is the arm, to the lower side of which is fastened the prism-box. On 

 the upper horizontal surface of this is the nose-piece, with an extra 

 adapter for high powers, and in the oblique surface is a screw-socket 

 for the body-tube. 



To transform the instrument into an ordinary Microscope, fig. 3, the 

 tube is unscrewed, the milled head at the front of the arm loosened, which 

 releases the prism-box, and the arm is swung on its axis from between 

 the pillars into an upright position. The tube is now attach :d to the 

 opposite side of the nose-piece, and after the stage clips are reversed it 

 is ready for work. 



The " University " Microscope (figs. 4 and 5) is in its general con- 

 struction similar to the preceding, except that the (single) pillar and the 

 arm are not japanned but are of brass, and that the instrument swings on 

 an axis vv^hich is the same as that of the mirror-bar. The stage consists of 

 a glass plate mounted in a brass ring. 



The prism used for inversion is that suggested by Mr. J. Lawrence Smith 



* ' Illnstrated Catalogue of Microscopes, Objectives, and Accessories,' lOth ed., 1886, 

 p. 3.3. 



