J. MATTHEWS ON THE MICRO-MEGASCOPE. 169 



of the window of the room when used bj daylight. Here, then, 

 was the germ of the invention lying unnoticed for want of develop- 

 ment. 



I believe that some time ago Mr. James Smith showed this 

 method of using an objective on the substage, but, as I am informed, 

 no more was done with the apparatus than to show opaque objects 

 well illuminated, and its uses were thus much restricted, no mirror 

 or prism having been used. 



Lastly, on examining my plan of using the plane mirror critically, 

 I found that, in every case, there was a slight confusion of the two 

 images given by its first and second surfaces. In a large proportion 

 of cases this is of no consequence, but in some it certainly does 

 more or less impair the definition. I have, therefore, caused a right- 

 angled prism to be fitted up in its place, the reflections from which 

 leave nothing to be desired, either in definition or light. It will 

 readily be seen how valuable this plan may become in drawing, the 

 size and scale being wholly at command, and if the instrument be 

 placed horizontally, neither mirror nor prism are required. I have 

 called the instrument a Micro- megascope, because we have with it 

 the power of either magnifying or diminishing an object at will. 



