344 
MR. AIRY’S ACCOUNT OF THE HARTON EXPERIMENT 
- incessant sequence, as in the observations at Harton. The uncontrolled conduct of 
the experiments was entrusted to Messrs. Dunkin and Ellis ; and I am confident it 
will be found that they are inferior to none that have ever been made. 
In all cases, the fires for warming the rooms were lighted nearly twenty-four hours 
before the observations began. 
67. When the pendulum-boxes were opened at Greenwich, two of the four thermo- 
meters which had been used at Harton were missing, and all attempts to trace them 
have hitherto failed. Two thermometers belonging to the Royal Observatory (one 
by Thomas Jones and one by Troughton and Simms) were substituted for them. It 
would have been desirable to use the very same thermometers which were used in the 
Harton experiment ; but it is probable that, with the considerable range of tempe- 
rature used in these experiments, the accidental differences between two thermometers 
made by makers of repute will not produee any sensible effect on the result. 
68. The following is the journal of operations : — 
Fifth Series. Pendulum 1821 in heat. 
Observations commenced a little before noon. Mr. Dunkin observed 
Pendulum 1821 from the beginning of Swing 83 to the beginning 
of Swing 85. Mr. Ellis observed Pendulum 8 from the beginning 
of Swing 83, and 1821 from the end of Swing 85, to the beginning 
of Swing 87. 
Mr. Dunkin observed 8 from the end of Swing 87 to the beginning of 
Swing 89 ; Mr. Ellis observed 8 from the end of Swing 89 to the 
beginning of Swing 91 ; and Mr. Ellis observed it from the end 
of Swing 91 to the end of Swing 92. Mr. Dunkin observed 1821 
from the end of Swing 87 to the end of Swing 92, nearly two hours 
after midnight. This closed the Fifth Series. 
Sixth Series. Pendulum 8 in heat. 
Jan. 4. — Commencing about 1^ hour before noon. Mr. Dunkin observed 1821 
from the beginning of Swing 93 to the beginning of Swing 97. 
Mr. Ellis observed 8 from the beginning of 93 to the beginning of 
95 ; Mr. Dunkin from the end of 95 to the beginning of 97. 
Jan. 5. — Mr. Ellis observed 1821 from the end of 97 to the beginning of 99; 
Mr. Dunkin from the end of 99 to the beginning of 102 ; Mr. Ellis 
at the end of 102. Mr. Ellis observed 8 from the end of 97 to the 
end of 102, about 1^ hour after midnight. This closed the Sixth 
Series. 
1856. Jan. 1.— 
Jan. 2. — 
