TABLE X.

Relative Effect of Cold on Oils.

Temp. -15° C. (= 5° F.) Time of Exposure = 6 hours

SYMBOLS ACCORDING TO TABLE III.	CONDITION OF OIL.
TIME.	15 MIN.	30 MIN.	1 HOUR.	6 HOURS.	ORDER OF VISCOSITY
E. K. W. w.	...	...	...	...	2
W. F. N. w.	...	...	t-f.	t-f.	4
D. C. S. w.	...	...	...	...	2
D. C. S. ch.	...	...	...	...	2
D. C. S. cl.	s-s.	s-s.	s-s.	s-s.	6
W. C. w.	...	...	...	...	2
B. & K. w.	...	...	...	...	2
S. B. & Co. w. c.	...	...	...	...	1
C. L. Co. w.	s-s.	s-s.	s-s.	s-s.	5
C. L. Co. No. 1.	s-s.	s-s.	s-s.	s-s.	7
Glyc.	...	...	...	...	1
Alb. f.	...	...	...	...	3
Sp.	s-s.	s-s.	s.	v-s.	8
Ol.	v-t-f.	s-s.	s.	v-s.	9

T. F. = Thickly fluid; or like honey. V. T. F. = Very thickly fluid; or like jelly. S. S. = Semi-solid; or like butter at 60° F. S. = Solid; or like butter at freezing point. V. S. = Very solid; or like paraffin wax.

The figures in the last column denote the apparent relative viscosity, as ascertained by inverting the test tubes repeatedly.

Fig. 15

Again, even if the oil were viscous enough in high temperatures to resist the tendency to be "squeezed" out of the bearings, the rate of the timepiece would be seriously affected by the variation of solid and fluid friction—especially the latter—caused by a variable viscosity of the oil.

When a watch, chronometer or clock has been so adjusted as to keep a maximum even rate, the oil is one of the factors of the variation which has been overcome; and it is obvious that if another oil be used, in which a greater or less variation of viscosity exists than in the oil with which such timepiece was lubricated prior to adjustment, the variation so produced will be more or less observable.

It is, then, evidently necessary to be able to ascertain, with the greatest possible exactness, what change in this respect is produced in the various oils by a change of temperature. The means previously given (81-83) have their value; but when supplemented by a method for determining the particular property under consideration, the results obtained are exceedingly interesting and valuable. On account of the importance of this matter the author has made investigations in this direction, using a "viscosimeter" as shown at Fig. 15, and of which the following is a description:

AA represents an ordinary retort stand, with adjustable arms, BB, for holding in position the thermometer C, and the funnel DD capable of holding about one pint of water. EE is the viscosimeter proper, a glass tube, swollen at the lower end, and terminating in a circular orifice of 1 millimeter (= .04 inch) in diameter;[25] being a "pipette" holding one cubic centimeter of oil between the dotted lines U and O.

F is a flexible gum elastic tube fitting with an air-tight joint to the upper end of the glass tube. The funnel is closed at its lower end by a tightly-fitting cork H, in which an opening is made, through which opening the pipette passes and projects slightly below. G is a small, shallow vessel, preferably of glass, of sufficient capacity to receive the contents of the pipette. S is a syphon composed of a glass tube in two sections—united by a short piece of rubber tube on which the device P pinches by the adjustment of the lever L—the bent section beginning near the bottom of the funnel, while the straight section terminates below the level of the table on which the retort stand is placed.

In operating with this, the author proceeded as follows: The funnel was partially filled with water, and hot water added until its temperature reached 43° C. (= 110° F). A sufficient quantity of the oil to be tested was placed in the glass vessel G, and drawn into the viscosimeter by gentle suction of the mouth until it exactly reached the line U, where it was retained, by a slight pressure with the thumb and finger, for five minutes, the temperature of the water in the funnel being kept constant. At the end of that time, after being sure that all the conditions as to temperature and quantity of oil were satisfied, the pressure of the thumb and finger was relaxed, when the oil began to drop through the lower end of the pipette.

The time required for the upper surface of the oil to fall from U to O was carefully ascertained by means of a "stop watch," and the number of seconds noted. In case of doubt the test was repeated.

The temperature of the water in the funnel was then lowered by the addition of ice, to 38° C. (= 100° F.), when the operation was again performed as just described. This was repeated at regular intervals of temperature down to 4° C. (= 40° F), when the water was again heated, the pipette thoroughly cleansed by introducing benzine into the pipette in a manner similar to that by which the oil was introduced. The surplus water which accumulated in the funnel was allowed to escape through the syphon by relaxing the lever of the pinching device. It is obvious that the number of seconds, in each case, corresponds to the viscosity. Other oils were put through the same course, the results obtained being shown in table XI.