1892.] THE MICKOSCOPE. 163 



demonstration, chiefly of continental microscopy, too large to be 

 seen satisfactorily in many days, or, when seen repeatedly, to be 

 remembered in its details as one would wish. Few persons in- 

 terested in the microscope could have spent two or three weeks 

 in serious study of the exposition without beingi amply repaid 

 both in pleasure and in profit ; while they would certainly have 

 enjoyed, meanwhile, a delightful visit in the quaint and charm- 

 ing town. 



Historical Exhibit. 



Amidst the chaos of instruments displayed, a thoughtful per- 

 son naturally turns first towards the historic exhibit, and espe- 

 cially to the one microscope of unique claims and interest, the only 

 known original by Hans Janssen or his son Zacharias, who are 

 claimed to have invented the instrument in or about 1590. Upon 

 this claim rests the character of the exposition as a tricen- 

 tennial, and to the memory and honor of these modest Dutch 

 spectacle-makers the enterprise was oflicially dedicated in the 

 form '' To Hans and Zacharias Janssen, of Middelbourg, in- 

 ventors of the compound microscope, on the occasion of the 300th 

 anniversary of their admirable invention, the first cause of the 

 most important discoveries in the medical and natural sciences." 

 The Janssens must have experimented upon a variety of forms, 

 as was most natural under the circumstances. Their instruments 

 have commonly been described as tubes of gilded copper, one 

 inch in diameter and six feet long, being, probably, telescopes 

 converted into compound microscopes, supported by dolphin- 

 shaped pillars over an ebony base, on which rested the object to 

 be examined. One of these is said to have been carried to 

 England about the year 1590, and to have been shown to William 

 Borrell and others. Very diflerent and far more crude is the 

 '•'• ??iicroscope authcntique de Janssen " contributed to the expo- 

 sition by the Zealand Society of Sciences. This consists of rough 

 tin tubes, soldered, about two inches in diameter, and, when com- 

 bined as a microscope, some 13 to 14 inches long, containing an 

 ocular and objective, each consisting of a single lens of about three 

 inches focus. It has no stand, but is held in the hands and aimed, 

 telescope-fashion, at the object, which it magnifies from o to some 

 5 or 6 diameters, according to the extension of the tubes. Though 

 very rudimental, roughly fitted, and to our ideas, absurdly inef- 

 ficient, it is still evidently a microscope, and none the less so if 

 it was originally an experiment in telescope-making. Therefore, 

 conceding its genuineness, which, though attacked in the interests 

 of other claimants, does not seem yet to have been successfully 

 controverted, and that its maker was aware of the possibility and 

 eftbct of focusing it upon near objects, whigh is so probable as to 



