W. A, Rogers on Variability of Personal Equation. 303 
_ Thus, while the change is not large, every series of observa- 
tions gives the same sign. It will not answer, however, to as- 
sume, either that the mean value remains constant, or that 
another observer would find the same value, since several con- 
ditions contribute to the result found. In reading up the re- 
cords, the rather curious fact was noticed, that the probable 
error of observation was less for an abnormal than for a nor- 
mal position of the body. 
Tl, Does a change of’ temperature affect the personal equation ? 
Absolute. 
a 
Dec, 12 42°~—(—4°)—-+ -0368 Feb. 10. 
42°—(—4°)——-O14 Change. 
12 
12 42°—(—3°)=+°019 38°==-+0715 
12 3 B.—T. i iy? +105 0345 
Feb. 10 38°—(—s"—+079 | RT. A Er op 
bao Uk 
Feb. 10 38° —(—3°)—4--107 R.-B.} ot oe ee 
The observations for ordinary temperature were made in the 
Clock-room, For the low temperature observations, an aper- 
with gloved hands, the second and third with hands unpro- 
tected. It wi seen that in my own case, the change is 
slight, while with B, and T. it is large. The values depend 
Upon very careful observations continued through 20 revolu- 
tions of the cylinder, The probable error for high and low 
temperature did not sensibly vary with myself and B., but was 
about +-005s larger for low temperature in the case of T. : 
HL. Does an exhausted state of the system produce a variation of 
* 
personal equation ? 
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