24 THE AMERICAN MONTHLY [Jan., 



of the introduction of this model, there was no uniform- 

 ity in the design of microscope stands, and it appears to 

 me that this pattern succeeded in ousting- all others by 

 conforming in some degree, as described above, to the 

 proportions of the human body, much as a spectacle 

 frame is adapted to the face. One may be sure that for 

 continuous and laborious use, such as falls to the lot of 

 a professional worker, such an instrument as is least pro- 

 ductive of muscular fatigue will be most fruitful in 

 results. For it is evident that a man sitting at a table 

 in the attitude of work will have his eyes naturally situ- 

 ated about 14 in. above the table, and about 6 in. from 

 its edge, so that his arms, as they rest upon the table be- 

 fore him, will bring his hands close together in front, the 

 directions of his eyes falling upon them without con- 

 straint, at an angle of about 15° from the vertical. A 

 stand which falls into place within these dimensions will 

 save fatigue — an advantage for which much may be sac- 

 rificed in many kinds of work. With a weighted foot, 

 if produced slightly backwards, sufficient stability may 

 be gained for such a small degree of inclination, or the 

 vertical position will not be found extremely irksome, at 

 least to the professional worker. The breadth of the 

 hand regulates the height of the stage and its breadth ; 

 and the remainder of the space between the eyes and the 

 table is all that is available for the length of the tube. 

 Whatever opticians may say, those who have to econo- 

 mize labor will be found generally to prefer such a type 

 of instrument ; and the question arises whether it is more 

 probable that such a design should have originated in 

 the mind of an optician, or in that of a user of the micro- 

 scope. I incline to the latter opinion, and may inter- 

 pose the query whether any other reason can be given 

 for fixing the tube-length for which Continental objec- 

 tives are corrected at 150 mm. or thereabouts. 



In fig. 1 the first of the instruments described by 



