In the column for [eta] corrected the differences due to the use of different instruments are of course eliminated. The absolute viscosity of water at 15° C. determined in four different instruments is shown below. Poiseuille's value for water being 0.0122. --------------+-------------+-------------+-------------+-------------+ Instrument. | 1. | 2. | 3. | 4. | --------------+-------------+-------------+-------------+-------------+ [eta] corrtd. | 0.0109 | 0.01185 | 0.0124 | 0.0120 | of water. | | | | | K_{1} value.. | 0.000000898 | 0.000000863 | 0.000000932 | 0.00000052 | K_{2} value.. | 0.235 | 0.2175 | 0.226 | 0.0204 | --------------+-------------+-------------+-------------+-------------+ The above values for various gums and dextrins were obtained at a constant temperature of 15° C. and are compared with water at that temperature. It is of the utmost importance that the temperature of the water surrounding the bulbs should be adjusted for each series of experiments to the temperature at which the absolute viscosity of the water was determined. As far as we have ascertained, in gum solutions there is a steady diminution in viscosity with increase of temperature until a certain temperature is reached, beyond which increase of heat does not markedly influence the viscosity, and it is possible that above this "critical point," as we may term it, the gum solutions once more begin to increase in viscosity. The temperature at which the viscosity becomes stationary varies somewhat with different gums, but broadly speaking it lies between 60° C. and 90° C., no gums showing any marked decrease in viscosity between 80° C. and 90° C. The experiments we have made in this direction were conducted as follows. The 300 c.c. bottle containing the gum was placed in a capacious beaker full of hot water, and the viscosity instrument was also surrounded with water at the same temperature. Thermometers were suspended both in the beaker and the outer jar. The viscosity at the highest temperature obtained, about 90° C., was then taken and repeated for every fall of 4° C. till the water reached the temperature of the air.