68 Microscope Object-glasses and their Power. 



the breaking up of the most deheately lined scales into their 

 component molecules. 



It is noteworthy that these were the very first objects used to 

 test improving definition. These lines could be seen by minute 

 spherical lenses, and Mr. Wilhams, the Assistant Secretary of the 

 Royal Astronomical Society, lately informed me that formerly he was 

 able with lenses of his own manufacture, and which he kindly lent 

 to me, of about 1-lOOth of an inch full length, to distinguish not 

 only the lines of such scales, but even heads, at which he says he 

 got thoroughly laughed at in those microscopically benighted days. 

 The process by which definition has advanced seems identically the 

 same now as formerly. Diatoms and scales were at first merely 

 lined objects. In scales, next came a ladder-like appearance between 

 the ribs, just like that figured by Mr. Hogg on the scale of the 

 gnat's wing. An improving definition showed more numerous 

 transverse lines : as the glasses are better made, the intervals between 

 the lines appear molecular: the lines become ribs, and lastly the 

 ribs themselves give up then- component beads, formed generally 

 in two difierent planes. All these scales appear to be made upon 

 one type, a double agglomeration of molecular beading, more or less 

 regular in size, and more or less symmetrically arranged. Innu- 

 merable examples could be given of this. The finest scales of 

 Menelaus (morplio) transmit a bluish light, and the ribs yield two 

 sets of beads. 



Again, the tufted elongated scales of Hiijparchia Janerii give 

 up a very beautiful collection of reddish and bluish beads, as close 

 together apparently as grains in a sand heap, the bluish being 

 uppermost. 



( To be continued.) 



VI. — Microscope Object-glasses and their Power. 

 By Edwin Bicknell. 



In the * Monthly Microscopical Journal' for Nov. 1871, I made 

 some " remarks " on Dr. Woodward's " Note on the Eesolution of 

 Amphipjleura pellucida by a Tolles' 3^th." In those remarks I said 

 that I considered it nothing more nor less than deception in Powell 

 and Lealand in putting out objectives of that power as a ^J■\^i, and 

 that Dr. Woodward was no less guilty of the same in knowingly 

 sending out work done by that objective as the work of a y^th. 

 Mr. Wenham has taken me to task for making that statement, 

 and thinks it hardly fair, and discourteous to tlie gentleman named. 

 I should not have known the power of the so-called ^\^th, if Dr. 

 Woodward had not given the data ; and while he was very par- 



