THE AMERICAK MONTHLY 



[May, 



meaning. As a concrete thing, it is 

 the written recoi^d of the experience 

 and opinions of men trained in ob- 

 servation and in logical methods of 

 thought. .... 



It is said that pieces of glass shaped 

 like lenses have been found in the 

 ruins of Assyrian towns, but if so 

 their use was forgotten. The year 

 1590 is the first date that can be as- 

 signed with certainty to the first mi- 

 croscope, a huge thing like a dwarf 

 telescope with dolphins for legs. In 

 1665 small globules of water were 

 used, a device that may be imitated 

 by a pill-box with a pinhole in the 

 top and a drop of water in the pin- 

 hole. In 1673 Sir Isaac Newton 

 made a reflecting microscope on the 

 principle of the reflecting telescope. 

 But so little hope did any one have 

 of the successful application of the 

 principle of achromatism, or the cor- 

 rection of lenses, then newly dis- 

 covered by Euler, that so late as 1821 

 the construction of a good achromatic 

 instrument was regarded as impossi- 

 ble. 



The modern microscope dates from 

 1829, when Lister discovered the 

 methods of aplanatic correction. 

 Since his discovery there has been a 

 steady improvement in the construc- 

 tion of lenses, which has not yet 

 reached its limit. So short a time 

 has elapsed since the construction of 

 the first compound microscope, that 

 its entire development has been ac- 

 complished in a single lifetime. One 

 of the most agi-eeable personal remi- 

 niscences of my life was a meeting 

 with Dr. Carpenter, of London, the 

 well known author of ' Carpenter's 

 Physiology,' and other valuable 

 works, at Montreal, in 1882. Him- 

 self one of the leading inicroscopists 

 of our time, he described the various 

 steps in the improvement of the mi- 

 croscope and the more important 

 discoveries made by it from personal 

 observation and participation ; being 

 one of those of whom it might par- 

 ticularly be said that he was there 

 and a part of it, having seen, and had 



a share in, the improvement of the 

 microscope from the very earliest be- 

 ginnings. 



The limit of vision was placed by 

 Ehrenberg at ^J-g- of an inch, that be- 

 ing the smallest object we can see 

 with our naked eye, but with the 

 most powerful instrument it may now 

 be placed at a little over 100,000 lines 

 to the inch. What this means it may 

 help you to discover if you consider 

 that an inch enlai'ged in like propor- 

 tion would measure one mile and a 

 half, or reach from here to the Capitol. 



Probably there are not a dozen 

 persons in the world at any one time 

 who are competent to make a first- 

 class, high-power objective, and any- 

 thing that is so rare must necessarily 

 command a high price. 



The most expensive tools are not 

 at all necessary to do good and valua- 

 ble work with the microscope, or to 

 obtain from it an immense amount of 

 enjoyment. This latter use of the in- 

 strument is one that people are only 

 just beginning to find out, and we 

 hope to give you this evening some 

 of the pleasure that any intelligent 

 mind receives from looking into a 

 new world, where everything is not 

 only new and strange but in many 

 cases wonderfully beautiful. Among 

 the things you will see are some of 

 the diatoms whose sui'facesare marked 

 with a fine net-work of carving in 

 patterns that rival the finest lace in 

 geometrical accuracy and intricacy, 

 the surfaces of crystals that glisten and 

 glow like polished gems, and, most 

 beautiful of all, the wonderful eftects 

 pi-oduced by polarized light, which 

 furnishes us with a means of analysis 

 whereby the most minute molecular 

 structure of matter is made known. 

 But the microscope is far from being 

 only a pretty toy or a means of seeing 

 pretty things. It is not an extrava- 

 gant statement that our knowledge of 

 the physiological action and minute 

 anatomical structure of living beings 

 is wholly built on the use of the mi- 

 croscope. In 1636 Dr. Harvey held 

 I many and long arguments to prove 



