THE AMERICAN MONTHLY 



[October, 



good qualit}' ruled on glass were stated 

 thus : " A perfect line is densely black, 

 with at least one edge sharply defined. 

 Both edges are perfectly smooth ; add 

 to these characteristics a rich, black 

 gloss, and you have a picture of the 

 coarser lines of a perfect Nobert 

 plate. In the study of the action of 

 a diamond in producing a breaking 

 fracture in glass, the microscope seems 

 to be of little service, but we can call 

 it to our aid in the study of its action 

 in ruling smooth lines. One would 

 naturall}^ suppose that a line of the 

 best quality would be produced by the 

 stoppage of the light under which it 

 is viewed by the opaque groove which 

 is cut by the ruling diamond. With- 

 out doubt this is the way in which 

 lines are generally formed. But it is 

 not the only way in which they can be 

 produced. An examination under 

 the microscope will reveal the fact, 

 that in some instances at least, a por- 

 tion of the glass is actually removed 

 from the groove cut by the diamond ; 

 and that the minute particles of glass 

 thus removed are sometimes laid up 

 in windrows beside the ruled line, as 

 a plow turns up a furrow of soil . . , 

 The particles of glass removed take 

 one of four characteristic forms : (a) 

 They appear as chips scattered over 

 the surface of the glass. (^) They 

 appear as particles so minute that 

 when laid upon a windrow and form- 

 ing an apparent line they cannot be 

 separated under the microscope, (c) 

 They take the form of filaments when 

 the glass is sufficiently tough for them 

 to be maintained unbroken, (d) They 

 take a circular form. . . . It must not, 

 however, be supposed that lines of 

 the best quality always present the 

 appearance described above." 



Mr. Fasoldt's claim that he has suc- 

 ceeded in ruling one million lines to 

 the inch received attention. Con- 

 cerning it Prof. Rogers said; "It is 

 only fair to say that until recently I 

 have shared in the general incredulity 

 with which Mr. Fasoldt's claim has 

 been regarded. Indeed, I still think 

 he has placed the limit just a irifie 



too high. But if the limit is reduced 

 one-half, I am by no means sure but 

 that it may be reached." After a dis- 

 cussion of the subject of the resolu- 

 tion of lines, this test was proposed : 

 " Let us then have a test which will 

 forever set at rest this vexed question 

 of resolution. I submit for vour con- 

 sideration the following outline of a 

 test which I venture to think will be 

 sufficient and conclusive : Let Mr. 

 Fasoldt rule three plates under as 

 nearly the same conditions as possible, 

 except in the number of lines in the 

 different bands of each plate. Let 

 him label each plate and accompany 

 it with a full description of the num- 

 ber of lines in each band. Let these 

 plates be sent to any gentleman in 

 whom the great body of microscopists 

 have confidence as eminently qual- 

 ified to conduct an investigation of this 

 sort, such as Prof. H. L. Smith of 

 Geneva, or Col. J. J. Woodward of 

 Washington. Let whoever receives 

 the plates remove the labels of Mr. 

 Fasoldt and put in their place labels 

 whose signification is known only to 

 himself. Then let the gentlemen who 

 think they have resolved 152,000 lines 

 to the inch take the plates, make their 

 count of the lines in each band, and 

 send in their report. Let the plates 

 also be photographed, and let the 

 number of lines be counted : then let 

 the results of these investigations be 

 published. If all substantially agree 

 in the count, this will end further dis- 

 cussion." 



Prof. A. H. Chester explained at 

 length his new method of dry mount- 

 ing with the cover-glass removable. 

 " The object is fastened to the glass 

 slip in the usual way and a cell built 

 up around it by means of one or more 

 tin rings. When the cell is high 

 enough so that the cover-glass laid on 

 top will not touch the object, a tin 

 ring having a little larger hole is ce- 

 mented on, thus forming a ledge on 

 which the cover-glass may rest, with 

 room above it for the wire ring which 

 holds it in so firmly that there is no 

 danger of its being jarred out." The 



