156 
DE. T. E. EOBINSON AND ME. T. GEUBB’S DESCEIPTION OF 
construction. It is impossible to contemplate without enthusiasm the treasures of dis- 
covery which are opening before the accomplished astronomer who is about to sweep, 
with an instrument that has but one superior in the world, a sky whose wonders only 
one has yet explored, in a climate such as British astronomers can only dream of. 
What strange nebular forms it may reveal, what new configurations of stars, what new 
cosmical laws it may unfold, what new elements it may disclose, we soon shall know ; 
and the fulfilment of these high anticipations will I am sure be the best compensation 
to the maker of this noble telescope for all the thought and toil which were required 
to make it what it is j and also, may I be permitted to say, to the three whom the 
Society associated with him in this great work, and who, though in a far inferior mea- 
sure, shared with him the intellectual labour and the anxieties connected with the 
task. Even the practical experience which has been gained in its construction is a 
precious addition to our knowledge: and in this belief we have thought it right to 
put on record its leading facts. They who, as I hope, will hereafter try to equal or 
surpass the Great Melbourne Telescope will not think these details tedious. Even they 
who have no special interest in optical or mechanical science may be reminded that every 
well-established fact, everything which extends man’s control over the inert masses or 
the energetic forces which surround him, is an element of power, is an agent whose po- 
tency may extend far beyond his ken, is an everlasting possession of the human race. 
Appendix No. I. 
Bate of Cooling of the Specula. 
[Eig. 42. A represents the temperature-curve of the first speculum, B of the second, and 
C the mean of the two. The abscissas are the number of days from the casting to the 
removal of the specula from the oven ; the ordinates are the degrees of the galvano- 
meter. The temperature of A when removed was 7 0°, about 5° above the air, that of B 
w r as 72°, about 20° above the air. The oven, when they were introduced, was believed 
to be between 900° and 1000°.] 
The irregularities in these curves are probably due to changes in the masses of iron 
which were in the vicinity of the galvanometer. The equatorial was about 200 feet 
distant, and underwent little change at this time ; but other parts were in process of 
construction at about 60 or 70 feet distance. 
No. II. 
[Some facts as to the time of grinding the speculum A may be useful. It was com- 
menced October 27. In four hours two-thirds of the surface was in action; in fourteen 
the whole surface was working, a proof how truly it had been cast. On October 29 a 
small hollow, Q‘25 inch diameter and 0*048 inch deep, was made by a copper drill and 
emery. When measured next morning the amount ground off was known. This was 
repeated daily, and it was found that 
