1881. ] 7 Microscopy. 931 
32°, only assists the operation) may be blown up with little 
fatigue through the tube, to effect a thorough intermixture of un- 
equally heated layers in the water stratum. The determination 
of the temperature of the disappearance of the bubble is easily 
obtained within five minutes, and that of its reappearance in about 
the same time. A low-power objective may be carefully wiped 
if its anterior lens is dimmed by flying drops or by rising vapor, 
when a high temperature is being attained ; but it is best to in- 
sert the whole objective in a small, narrow glass beaker floating 
upon the surface of the bath over the preparation. * ie 
place of the flowing tube a little agitator or churn at the end of 
the box had been previously tried, to produce the intermixture of 
the contents of the bath, but was given up on account of the in- 
convenient vibration and frequent dislodgment of the slide.” 
A still simpler apparatus was found to be more convenient 
when high temperatures were not required. In this case a plate 
of copper or brass 23 centimeters long, 6.5 centimeters wide, and 
I millimeter thick, with a central aperture of 2.5 centimeters, 
partly wrapped in pasteboard to prevent radiation, was laid upon 
the stage of the microscope. Over the central aperture was 
cool water to the bath, while the eye remains at the eye-piece, and 
a steady current of air is blown through the glass tube; with this 
apparatus, which may be called the immersion warm bath, it mat- 
ters little, for most purposes, what liquid, stand or objective 1s 
€mployed; and there is no difficulty in obtaining, satisfactorily, 
the two determinations within ten minutes, to an approximation 
of about one-twentieth of a degree. These forms of apparatus 
May be of service in other branches of thermal microscopy where 
an exact determination of the temperature applied is desirable. 
- Deatn or Cuartes A. Spencer.—Those who work with the 
Microscope, or enjoy its teachings, will not soon forget that they 
have lost a friend in the death of this remarkable man, whic 
ccurred at Geneva, N. Y., on the 28th of September. Almost 
Without preliminary education, he undertook the manufacture of 
_ Microscopes, with little knowledge of the experience of others in — 
