SCIENCE. 



97 



SCIENCE: 



A Weekly Record of Scientific 

 Progress. 



JOHN MICHELS, Editor. 



Published at 

 229 BROADWAY, NEW YORK. 

 P. O. Box 3838. 



SATURDAY, MARCH 5, 1881. 



MICROSCOPES AND THEIR OBJECTIVES. 



We are told by one maker of microscopes that he 

 has orders in advance which will prevent his under- 

 taking new work for at least four months from the 

 present time. Supposing his statement to be true, 

 and we heartily trust it is, it would appear to show that 

 the number of those undertaking microscopical inves- 

 tigations is largely on the increase, and as the prob- 

 abilities are that many of those now investing their 

 money in microscopes and objectives, are doing so with 

 little experience to guide them in their selection, it 

 may be useful at this moment to take a review of the 

 microscope market. 



The purchase of the microscope stand and the ob- 

 jectives to use with it will be considered separately. 

 They are usually purchased together, but there is no 

 reason for doing so, and we would like to see each 

 handled by a distinct branch of trade. To make a 

 good microscope stand needs only the skill of a good 

 worker in brass, under suitable direction. On the 

 other hand, the manufacture of objectives, and the 

 other optical parts of a microscope, requires the 

 skilled labor of an optician. 



In regard to the microscope stand, we would state 

 that many improvements have been recently made, so 

 that to avoid being saddled with one which may be 

 considered obsolete, it would be as well to go directly to 

 one who manufacturers his own stands, and direct him 

 to make one to order ; by so doing, the additional ad- 

 vantage will be secured of obtaining an instrument 

 specially suited for particular work — a very important 

 point. 



The temptation is great to name one or two 

 microscope stands which, in our opinion, are perfect in 



workmanship, designed on the best model and, withal, 

 quite moderate in price ; but to do so would court 

 misinterpretation of our motives ; so we may state that 

 such firms as Bausch & Lomb, Beck, Bullock, Gru- 

 now, Schrauer, Slidel, Zentmayer, are all reliable Am- 

 erican manufacturers, and that most of these firms 

 now produce such an instrument as we would advise, 

 at a cost of about 40 to 50 dollars for a Monocular 

 stand, not including accessory apparatus or objec- 

 tives. We have just seen an instrument, for the latter 

 price, having perfection of workmanship and the latest 

 improvements. 



In regard to microscope objectives, the greatest 

 caution should be employed by the inexperienced 

 at this moment, for after twenty-five years experience 

 in purchasing objectives, the present price-lists of 

 opticians appear to us a perfect chaos of quotations. 



In the first place, the objection has been raised by 

 purchasers that object glasses of a certain focal length 

 and stated aperture, vary in their linear magnifying 

 power, among different makers, so that a quarter-inch 

 which, for instance, should give 200 diameters with an 

 A eye-piece, is found to be a 4-10, allowing only 120 

 diameters if purchased of another maker, or perhaps it 

 will give 225 diameters similar to a i-5th, when ob- 

 tained from a third manufacturer — even when the con- 

 ditions are alike. This, no doubt, originated in one of 

 the tricks of the trade. A makes a i-4th which, in 

 resolving power, equals the i-6th of B ; in conse- 

 quence, A claims at once a superiority of workman- 

 ship, and perhaps secures a reputation for objectives, 

 when, if the truth was known, the i-4th was in fact 

 a i-6th. 



It must be remembered also that all objective", 

 vary in quality even from the same maker, and that 

 one may be given to an inexperienced person which is 

 very far from the supposed standard of excellence ; 

 with some makers not more than one in twelve would 

 be accepted by an expert. 



Lastly, there appears to be a feeling that consider- 

 able improvements are imminent in the manufac- 

 ture of objectives, rendering those of yesterday 

 commercially valueless. If we may judge by a price 

 list just forwarded, a panic appears to have commenced 

 among those holding objectives made as recently as 

 four years ago. By a circular, we are informed that 

 the objectives of one of the most esteemed makers 

 are now offered at prices 50 per cent, lower than those 

 charged by the maker. " These lenses are of the best 

 quality and perfectly new" " simply to close out our 

 stock of these objectives." This offer is made by an 

 optician in the same city with the original maker. Ob- 

 jectives which cost $150 can be had for $75, and 

 others as follows: $110 for $55, $50 for $30. $40 for 



