ON THE EaUATORIAL TELESCOPE. 
339 
equatorial circles. Tliis may be obviated by making the tube of 
the telescope of thin brass, and by placing the object end a 
little farther from the point of suspension than the eye-end ; 
and by making the horizontal circle a little larger in diameter, 
and of a very considerable thickness ; or by merely exteuding- 
the screws which support the instrument to a greater distance 
from each other. But even though tliese piecautions were not 
taken, no great inconveniency will happen j as the telescope 
may be set to a very high elevation, vsithout any danger of 
overturning the instrument. To prevent all possible danger of 
this kind, the adjusting screws which support the instrument, 
may be let into a socket, fixed on the pedestal, about half an inch 
deep, and a slight degree wider than the diameter of the 
screws, they may also be attached, hy means of a silk cord, or a 
flexible piece of brass, to strong brass pins, fixed near the top of 
the pedestal.-— That all the above suggestions may very easily 
be brought into effect I have experimental proof. 
Such an instrument, I presume, could be atforded for iG ENtiinato tliat 
guineas. The data on which I proceed in this estimate are 
these: the instrument alluded to above in its original state, afiprded for 16 
, . . . r 1 . Kuiiiias. 
previous to its receiving most of the improvements now sug- 
gested, cost 13 guineas: allowing 2 guineas for the value of 
the small telescope, will reduce the expence of the equatorial 
circles to 11 guineas ; and allowing 5 guineas for the larger 
telescope now proposed, which is certainly not below a just 
estimate, the amount will be, as already stated, l6 guineas, 
which is not much above tlie price of a 2^ feet achromatic 
telescojre mounted in brass. Nor ought it to form any objec- 
tion to this proposal, that thcic would be fewer orders for 
larger instruments of this kind •, as gentlemen of fortune to 
whom 80 or 100 guineas is no object, and the directors of 
public observatories, will always prefer instruments of the 
largest and most acciv'ate construction ; and most of those who 
might purchase such an instrument as the above, would probably 
have never thought of purchasing any other instrument ol the 
kind. I know several gentlemen who would probably put- 
eha-'v 
