5^3 
Balls . — Temperature and Growth. 
over the cover-slip and slowly raise the temperature of the object. The 
rate of heating can be arranged for by adjusting the size and position of 
the flame. This method is very satisfactory in practice in spite of its 
crude appearance ; the temperature of the cover-glass rises uniformly and 
the rate of heating can be adjusted after a little practice ; it is not suitable 
for constant temperature work, for which a water-bath should be employed 
Fig. 3. Semi-sectional elevation of microscope and chamber. 
Inspection of the records transcribed at the end of the paper will 
show its efficiency. Irregular gas pressure in the laboratory mains is the 
cause of the uneven heating shown in the first curve. 
Temperature Measurement. Measurement of temperature is effected by 
Blackmans thermo-electric couples 2 , using the method of balance. 
One couple is varnished and embedded in a thin plate of 6o°C. M. Pt. 
wax, and immersed in a water-bath. The ends of the couple pass into 
2 Blackman and Matthaei, Proc. Roy. Soc. B., 1905. 
Qq 2 
1 See curves given below. 
