228 H. CROUCH ON MICROSCOPY IN THE UNITED STATES. 



English and American makers — who, I presume, like other manu- 

 facturers, make and sell what they find to be most in demand — have 

 almost entirely adopted this form for all instruments to which 

 accessory apparatus is required to be applied. 



It is essential that this distinction should be noted, because, if 

 you enquire of the enthusiastic supporter of the Continental model, 

 you will find that he rarely, if ever — for his particular class of 

 work — requires more than the most elementary form of stand, and he 

 often knows absolutely nothing about the proper illumination of an 

 object, the amount of dogmatism displayed being, as usual, in exact 

 proportion to the observer's ignorance of the subject. He knows that 

 to see something of a transparent object he must make use of the 

 mirror, and that it is of advantage to apply a condenser when 

 examining an opaque object. The polariscope is looked upon as 

 altogether beneath notice, being only fit for the amusement of 

 children. Dark ground illumination ! Well, it does not do to 

 profess absolute ignorance, but if you hand our observer a Wenham's 

 paraboloid, and ask him to apply it, his helplessness is at once 

 apparent. 



Possibly you may think this an exaggeration, but I can only 

 assure you that such cases have come under my notice again and ■ 

 again, one of the latest instances being that of an eminent German 

 microscopist, who assisted in examining the microscopes on exhibi- 

 tion at Philadelphia, and who from the first loudly proclaimed the 

 uselessness of binoculars, and the absurdities of English microscopes 

 in general, but whom we afterwards found out had never used one, 

 and who also had never heard of dark ground illumination. As the 

 result, however, of his experience there, his views were considerably 

 modified. 



In comparing stands of American and English manufacture, there 

 are one or two points of difference in general construction that are 

 worth attention, the most noticeable, perhaps, being that in the 

 American patterns the " limb" is generally supported upon a 

 single pillar ; whereas the English makers, with one exception, find 

 the double uprights or pillars more often preferred. The stages of 

 the American instruments are generally made of glass, and without 

 concentric rotation or mechanical adjustments ; whereas, as you are 

 aware, the majority of English microscopes are now made with 

 rotating stages, and a large proportion are also provided with 

 .nechanical adjustments. American makers have also generally 



