A group of papers on aspects of the manufacture of the 

 microscope was then read by Mr* Conrad Beck, Mr. F, 

 Watson Baker and Mr. Powell Swift, and discussion on 

 these papers ensued. 



A STANDARD MICROSCOPE. 

 By Conrad Beck. 



The British Science Guild having prepared a specification for 

 a standard microscope, we have been engaged for a year in working 

 out the manufacturing processes necessary to produce on a productive 

 scale a microscope that should fulfil the requirements of tnis specifi- 

 cation. The instrument has also certain additional new features 

 which will be appreciated by microscopists. 



The stand, limb and body are of a very solid, well-finished type, 

 with the horseshoe base, jointed pillar and Jackson-shaped limb. 

 The base and stage are both coated with a thick surface of ebonite, 

 the body has a larger tube than is customary; the drawtube is 

 graduated, and gives a mechanical tube length of from 140 to 200 

 millimetres. The standard length of 160 mm. has been adopted 

 for which all object glasses are corrected. The thickness of cover 

 glass for which dry object glasses are corrected is .15 mm., or 

 .006 inch. All object glasses except the very lower power are of 

 such lengths as to be in focus when used on a nose-piece or an 

 objective changer. The fine adjustment is of entirely new design, 

 the two milled heads, one on each side of the limb, are on the came 

 axis, but each milled head actuates a different lever, and thus there 

 are two different speeds, one of which is double as fine as the other, 

 both of which are always in operation. The convenience of this is 

 apparent to those who use object glasses of different powers. A 

 fine adjustment that is sufficiently fine for delicate examinations 

 with 1/12 object glass is frequently troublesome in focussing 1/6 inch. 



The action of the slow motion is by a screw with a point imping- 

 ing on a lever. This method has been considered, and iri our opinion 

 correctly so, the only known method of obtaining an absolutely free 

 movement without sag or backlash. 



The base of the microscope is provided with three rubber pads 

 which remove vibration, but which can be detached if a rigid 

 contact with the table is preferred. 



The instrument is supplied in its simplest form with a plain 

 tubular substage with an iris diaphragm, but t"his substage can be 

 removed by the microscopist himself and replaced by any of the 

 three more elaborate forms of substage, thus converting the instru- 

 ment into a complete bacteriological or research instrument. 



With the same end in view, a detachable mechanical stage can 

 be attached at any time by the worker himself. All parts are made 

 to standard gauges. 



