1887.] C. Piazzi Smyth on the Eclinlurgh Equatorial. 15 
shall be made of what is described in the previous pages, and by 
whomsoever the work may be carried out. 
(1) The present very thin flooring of the Dome will have to be 
propped up, substantially though temporarily only, before any 
heavy repairs begin. 
(2) The large timber blocking of Declination axis to be exchanged 
for a small, compact, iron apparatus, or say merely a steel rod, 
passing by two small holes through a thick part of the Polar axis, 
but leaving its ends standing out sufficiently to butt against either 
one, or other side of the great cradle-frame of said axis ; thereby 
serving the full purpose of the timber blocking, but without occu- 
pying one-hundredth part so much space, or fixing the Dome, or 
interfering with movements of workmen about the instrument. 
(3) Eevolving Telescope head, with all its weights and attach- 
ments to be removed ; Telescope tube to be raised 5 inches in its 
collars (from great mirror end, as assumed below, to eye-end above) ; 
great mirror to be restored, and residual balance at end of Declina 
tion axis (after being shortened 14 inches) to be practically ascer- 
tained as speedily as possible ; all superfluous weights being carried 
out of the Dome, noting how much. 
(4) The shutter of the Dome to be altered from present plan of 
pivoting in the Zenith, to Messrs Cook’s new plan of pivoting on 
the opposite side of base. The permanent opening of Dome being 
then taken right up to and 4 feet past the Zenith, with a breadth 
of nowhere less than 30 inches. A revolving ventilator of much 
larger diameter than the present one being then attached to the 
Zenith of the shutter, and three bull’s-eyes illuminators introduced 
beneath Zenith and horizon. A separate fence of sheet steel about 
3 feet high being made to slide horizontally across lower part of 
Dome’s opening, to keep out the violence of the wind when not 
observing at very low altitudes ; and the late Mr Grubb’s advice of 
lining the iron dome, with non-heat-conducting wood, to be no 
longer delayed. 
(5) All the air-passages in and around the pier in both Dome- 
room and under-Dome-room should be caulked with elastic tow, 
for otherwise both these rooms become a chimney of draughts to all 
the rest of the Observatory below their level ; and when shutters 
are opened there, the draughts up into the Dome are very severe. 
