CHAPTER VIII.

AT GREENWICH OBSERVATORY--1866 TO 1876.

1866

In this year the cube of the Transit Circle was pierced, to permit
reciprocal observations of the Collimators without raising the
instrument. This involved the construction of improved Collimators,
which formed the subject of a special Address to the Members of the
Board of Visitors on Oct. 21st 1865.--From the Report to the Visitors
it appears that "On May 23rd 1865, a thunderstorm of great violence
passed very close to the Observatory. After one flash of lightning, I
was convinced that the principal building was struck. Several
galvanometers in the Magnetic Basement were destroyed. Lately it has
been remarked that one of the old chimneys of the principal building
had been dislocated and slightly twisted, at a place where it was
surrounded by an iron stay-band led from the Telegraph Pole which was
planted upon the leads of the Octagon Room."--"On consideration of the
serious interruptions to which we have several times been exposed from
the destruction of our open-air Park-wires (through snow-storms and
gales), I have made an arrangement for leading the whole of our wires
in underground pipes as far as the Greenwich Railway Station."--"The
Committee of the House of Commons, to whom the Greenwich and Woolwich
Line of the South Eastern Railway was referred, finally assented to
the adoption of a line which I indicated, passing between the
buildings of the Hospital Schools and the public road to
Woolwich."--"The Galvanic Chronometer attached to the S. E. Equatoreal
often gave us a great deal of trouble. At last I determined, on the
proposal of Mr Ellis, to attempt an extension of Mr R. L. Jones's
regulating principle. It is well known that Mr Jones has with great
success introduced the system of applying galvanic currents
originating in the vibrations of a normal pendulum, not to drive the
wheelwork of other clocks, but to regulate to exact agreement the
rates of their pendulums which were, independently, nearly in
agreement; each clock being driven by weight-power as before. The same
principle is now applied to the chronometer.... The construction is
perfectly successful; the chronometer remains in coincidence with the
Transit Clock through any length of time, with a small constant error
as is required by mechanical theory."--"The printed volume of
Observations for 1864 has two Appendixes; one containing