98 THE NORTHERN MICROSCOPIST. 
bull’s eye condenser, and demonstrated how to adjust the bull’s eye condenser 
as an Amici prism, to shew the striations of diatoms. By this means 
P. Angulatum may be resolved by a ¥ in. of 60 degrees, and the A eyepiece. 
He described how the various methods of illumination might be obtained by 
means of cheap appliances, almost as accurately as by the most expensive sub- 
stage accessories. The objects shewn were 
Foraminifera (rare forms of.) Transparent. Illuminated with Bull’s- 
Hye Condenser as spot lens 5... ...2.2--020000+0seccdeeren semen aanaamaan 
Paramecium aurelia, illuminated with spot lens, shewing only very 
slight difference in the power of illumination as compared with the 
ADOVER oab'senscencsoeae ons odaiisdsleaneincececesatilnsden an slea eee te aan 
Pleurosigma angulatum, Resolved under ¥% in. objective, with the 
light transmitted obliquely <.......:.seccesds.0¢e-cedeet eye eee 
Foraminfera. Arranged insymmetrical groups. Opaque. The light 
from the lamp being transmitted through two bull’s eye condensers. 
By this means a more intense illumination is obtained............... 
Dr. A. Welsh exhibited an improved live cage, in two sections, designed and 
made by Mr. Spencer Smithson, of Facit. 
A vote of thanks to the hon. secretary for the use of his rooms brought the 
meeting to a close. 
NOTES AND QUERIES. 
Ponp Lire.—Will some reader kindly inform me where likely 
ponds for good finds are situate in or near Manchester ? and what 
is the most convenient form of case in which to carry a collecting 
bottle >—B. ‘ 
Dark GrounD ILLUMINATION.—In reply to W, he can produce 
dark ground illumination in various ways. First, by use of the 
bull’s-eye condenser, whereby a pencil of light is focussed upon the 
object by a lamp above; secondly, by fastening a circle of black 
paper upon the plane side of the bull’s-eye condenser, and placing 
it, flat side uppermost, underneath the stage throwing the light 
from a lamp upwards, by means of the mirror. A third method is 
that in which a half-inch objective is made to screw into an adapter 
fitted below the stage—this answers as an achromatic condenser, 
and, by stopping out the central rays with a small circle of blackened 
paper, dark ground oblique illumination will be obtained. I have 
not mentioned the Lieberkuhn’s and side reflectors, as W. does 
not seem to require anything special.—Venrvy Seward. 
Damar Mountinc Mepium.—-Dr. Carpenter, in his work on 
“the Microscope,” gives the following :— 
A.—Gum Damar, half-an-ounce; Oil of Turpentine, one 
ounce. Dissolve and filter. 
B.—Gum Mastic, half-an-ounce; Chloroform, two ounces. 
Dissolve and filter. Add A to B. 
This answers very well, but a much more simple plan is to dissolve 
