MEMORANDA. 199 



very high power, I have, for years, been in the habit of 

 using a low power as a finder, and then bringing the 

 object into the exact centre of the field (which is greatly 

 facilitated by the use of that neat contrivance, the moveable 

 pointer, without which no eye-piece is complete), change 

 the powers by screwing off the low power, and screw- 

 ing on a high one ; then, on bringing down the high 

 power to focus, if the achromatics are truly centred (which, 

 of course, they will be, if the maker has done his 

 duty), the desired object will still be found in the centre 

 of the field. This mode of finding, as I can amply 

 testify, is perfectly effective; but the heavy objection to it is 

 the figgle-niggling (I like expressive words) process of screw- 

 ing and unscrewing. Still I found it far better to do it than 

 to waste time in the tedious hunting I have described. 



Matters stood thus with me when I first heard of the 

 aforesaid " nose-piece/' Its construction was described to 

 me, and it was recommended merely for what it is in the 

 catalogues, viz., " a ready mode of changing one power for 

 another, without the trouble of screwing and unscrewing.'" 

 But I immediately saw further than that ; " for/' said I, " it 

 is evident to me that, if properly made, it must also be the 

 best ' finder' that can be used." 



Accordingly, having procured one, I w r as greatly pleased 

 to find my expectations amply borne out by fact ; and ex- 

 claimed, " This is the very thing I have so long been wanting : 

 EUREKA !" 



And I am in hope that I am the first who has " found it 

 out ;" I mean, this particular application of it ; for, as to 

 the said nose-piece itself, it is really nothing new, being, in 

 fact, merely a slight modification of the venerable old " six- 

 lens wheel," with which what we now call the "ante- 

 diluvian microscopes" were usually supplied. I have one 

 still by me, purchased more than thirty years ago; and 

 I have no doubt that, as the " march of improvement" 

 advances, we shall, in due time, have the full complement of 

 two-inch, one-inch, half, quarter, one-eighth, and one- 

 sixteenth, mounted and acting exactly on the principle of 

 a six-barrelled revolver. 



But to come to the practical application of the matter in 

 hand, — the power I recommend as a finder is one of those 

 luxurious one and a half inch powers made by Mr. Boss, 

 which exhibits a beautifully flat field, of great extent ; and 

 which I consider as low a power as we ever, practically, 

 require. 



On focusing with this, we shall, in many cases, see at one 

 view all the objects on the slider; but, if not, a slight move- 



