Dr. Goring oti Achromatic Microscopes. 415 



ceeded in making one exactly to his mind ; this will be a new 

 curiosity we shall owe to his genius ; the theory of it will 

 serve to amuse the learned. 



Mechanical Arrangements. — The merit due to the con- 

 trivance of these I hold to be but trifling ; I therefore am not 

 very ambitious to constitute myself a Sir Oracle concerning 

 them, and forbid every dog to bark when I speak on the 

 subject ; still less do I conceive myself justified in trespassing 

 on the pages of this valuable journal by entering into a de- 

 tail of my own particular whims about stands and apparatus, 

 which every maa will eternally alter, according to his own 

 ideas of utility and convenience. However, there are, I 

 think, certain principles which ought to be attended to, 

 whatever may be the manner in which they are carried into 

 ejOTeot. My own experience leads me to recommend the fol- 

 lowing punctilios to be observed in making a stand, &c. 



Thus, 1st, the bar and arm ought to be triangular, be- 

 cause, when pinched by a spring or other force on one side 

 only, they are sure to be locked fast in every other direction ; 

 which is not the case with square, flat, or round bars travel- 

 ling in corresponding sockets. 



2nd. The stage should be a fixture, both that it may not 

 give way during dissections, and that animalcules and aquatic 

 insects may not be disturbed by adjustments of any kind giving 

 motion to it during observation ; for when once unsettled and 

 lost from the field of view, it is often exceedingly difficult, and 

 sometimes impossible to find them again. The body, there- 

 fore, or single magnifier, should be able to travel completely 

 over the stage, and possess another motion independent of it 

 for adjusting the focus. 



3rd. The stage, in all other respects fixed, should be con- 

 structed to swing round on a pivot, with a clamp, that ob- 

 jects placed upon it may be viewed laterally as well as verti- 

 cally, and be made to remove altogether when occasion may 

 require, to allow of the introduction of large bodies, such as 

 an anatomical preparation, a jar of polypi, specimens of mi- 

 nerals and the like, to the operation of the microscope ; for 

 which purpose, it will be convenient that the bar should be 

 attached to the pillar of the microscope, in such a manner 



