226 



HARDWICKE'S SCIENCE-GOSSIP. 



optician, whose talents are of the first order, and 

 thinks we live in the golden age of these matters. 

 His character the reader will find is a complete 

 contrast to that of Mr. Oldbuck. Now it came to pass 

 that one wet day Mr. Oldbuck was walking up and 

 down in his study, occasionally surveying his wig in 

 a mirror, and somewhat ruffled in temper by the 

 impertinence of the junior members of a learned 

 body to which he belonged, who worried him till 

 (much against his will) he was forced to look into 

 a very fine achromatic ^engiscope, which showed 

 objects too well to please him. To vent his spleen 

 he was indulging himself in the following soliloquy: 

 ' What occasion have I or any man for any other 

 microscopes than single ones ? Was there ever any- 

 thing so ludicrously preposterous as forming the image 

 of an object and viewing by a species of microscope 

 called an eye-glass, instead of looking at the object 

 itself with an eye-glass ? Are we not content with 

 seeing Nature herself ? Would any rational being 

 rather behold a picture of a beautiful woman or 

 landscape than see the reality ? Away, then, with 

 this nonsensical trumpery, and let me alone with 

 my good old tried, staunch microscopes.' " 



Mr. Putty is now introduced, and a long argu- 

 ment ensues, Mr. Oldbuck sticking up for his single 

 lenses, and the former for his engiscopes. Mr. 

 Oldbuck is even unwilling to admit that any other 

 substance can be superior to glass, Mr. Putty 

 having asserted that by making lenses of other 

 substances of higher refractive and lower dispersive 

 power, they would be greatly improved. 



To which Mr. Oldbuck replies, that he could 

 never see any better through lenses made of dia- 

 monds or other precious stones than those made of 

 glass, and brings forward one of -£$ of an inch focal 

 length and 55° angle of aperture, using as a test 

 the scales of the diamond beetle, which, from their 

 brilliancy, would " ' show the aberration of the lens 

 if it had any ; but you see the scales perfectly clear 

 and distinct.' " 



Mr. Putty admits that the vision is clear and 

 satisfactory, but that the lines are not well made 

 out, and says he could show them much better with 

 an engiscope — " ' though I grant that I do not show 

 you the lines themselves, but only a picture of 



them, — so exact, however, that ' 



" ' It will not impose upon me. I do not choose 

 to trust to pictures, especially when I am exploring 

 unknown objects. Your engiscope (as you call it) 

 may do vastly well to exhibit known ones to a 

 parcel of women and children.' " 



Mr. Oldbuck continues to fight the ground 

 inch by inch ; and is asked if he will admit the 

 superiority of doublets and triplets over single 

 lenses, if he is shown something with them in a 

 decisive manner which he would scarcely be able to 

 see at all with one single lens out of twenty, and 

 then only in a very imperfect manner. But Mr. 



Oldbuck is not going to throw up the champion- 

 ship of the single lenses so readily, and tells his 

 antagonist, that 



" ' If you were to show me anything with another 

 instrument which I cannot see with them (single 

 lenses), I should be disposed to set it down as aa 

 illusion of some sort or otlier ; and if you were to 

 show me anything in a different manner from what 

 they show, I should be very much inclined to think 

 that they were right notwithstanding.'" (How 

 very thankful we ought to be that no such preju- 

 dice in favour of certain objectives exists in the 

 present day !) " ' Well, what is the wonder you are 

 going to show me ? I suppose it will turn out to be 

 the oblique lines on the brassica you are always 

 making such a fuss about— an isolated instance, 

 supposing the said lines to actually exist. I cer- 

 tainly have seen a few of the lines you allude to 

 with a doublet of about ^V of an inch focus. 



" Mr. Putty : ' Have you seen as much with any 

 of your adorable single magnifiers ? ' 



"'I have seen them occasionally when they have 

 been of very superior quality, and exquisitely set 

 with large aperture, but I freely own not with 

 sufficient distinctness to convince me of their ex- 

 istence. The appearance somewhat resembles the 

 tissue of a coarse piece of canvas, with the fibres 

 running diagonally, when it is placed too far off 

 from the eye to allow us to see the threads dis- 

 tinctly. The doublet makes this difference, that a 

 thread here and there seems stronger than the rest, 

 and therefore more distinct, but, as I have already 

 observed, I am strongly disposed to think the whole 

 an illusion produced by oblique light.' 



"'Have you seen the French brassica? The traces 

 on it are still more difficult to exhibit, or fainter 

 at least than those on the English variety, particu- 

 larly on that kind which is of the form of a heart, 

 or like the head and tail of the other kind, joined 

 together with the intervening parts on.' " 



Mr. Oldbuck is willing to admit for sake of argu- 

 ment that something can be said in favour of com- 

 pound magnifiers; he also agrees with Mr. Putty,[that 

 an instrument capable of resolving some difficult test 

 with a^low power is preferable to one requiring high 

 powers. Mr. Putty then introduces a new doublet 

 made upon truly scientific principles, being a com- 

 pound aplanatic lens of one kind of glass of Sir J. 

 Herschel : its focus is & of an inch. 



" ' Compound magnifiers, I believe, are at present 

 far from that state of perfection to which they are 

 capable of being brought, because the makers of 

 them are generally pleased to vie with each other 

 in trying who can insult science the most grossly 

 in the principles which they adopt, though I grant 

 that they work excellently well, according to them. 

 Kow, with this magnifier I think you will see tests 

 which cannot be discerned with any sort of single 

 lens, nor with this either, if you choose .to reverse 



