of the Bed Admiral Butterfly, and the Lepisma Saccharina. 63 



if widely separated and very brilliant, can be seen almost as easily 

 as lines, especially if the eye glances near them rather than at them 

 directly, as well known to astronomers. 



Nobert's New Bands are indicated to be from TT nro to TT njoirth. 

 of a Paris Line. Now, according to Babbage, the French foot is 

 equal to 1" 0657654 English foot, and the line is the 1-1 2th of 

 a pouce, which is the 1-1 2th of a French foot. By these data I 

 find the French line is 0-088813783 English inch, and not 

 • 088815, as generally given. This makes some difference in the 

 assigned English divisions per inch, and for those who may feel 

 interested in comparing the visibility of Nobert's Bands with rows 

 of spherules in contact of the same category, viz. so many to the 

 inch, I now add the result of some calculations accurately verified. 

 (The decimals are given merely to show the care taken.) 



A very careful examination of the ribs of the Atalanta Vanessa 

 (Red Admiral) has enabled me to distinguish the molecules of 

 which they are composed, viz. minute beads of the same size as 

 the transverse trios, crowded thickly together. Two rows of beads 

 to a rib would not exactly represent the appearance, as they are 

 arranged on a grooved surface, which, from the action of oil-drops 

 running along, seems to resemble a corrugated galvanized roof. In 

 many cases, when a little pressure has been applied to the dry slide, 

 the natural oil of the scale exudes. Under a Sixteenth, touching 

 the glass, the play of this oil is remarkable, and in my glasses 

 greatly improves the definition when it spreads between the scales 

 and the cover. I have seen these component beads, or molecules, 

 with a quarter condenser and an uncovered moderator lamp. 



On the Resolution of the Lepisma Saccharina Scale. 



The Lepisma Saccharina scale is far more difficult. 



1. The same arrangement with Powell and Lealand's new 

 |th immersion reduces the size of the ribs, making them finer than 

 inferior glasses, but with direct light they appear structureless; 

 between them, in the intercostal spaces, a faint irregular structure 

 is visible. Power 1200. 



With slight obliquity of illumination, these clear spaces began 

 to appear lumpy, broken up here and there with irregular bodies. 

 Removing the " quarter " condenser, I replaced it by Powell's achr. 

 condenser, one half of which was covered with green paper. After 



