Portable Equatoreals. 169 



will be in the field of view. On this occasion I might have been 

 forgiven if a blunder had taken place, as it is much more diffi- 

 cult to avoid such awkward result when any effort is made 

 to sustain a conversation and calculate at the same time ; but 

 luck favoured me, and having set the instrument, I had the 

 pleasure of requesting that the authoress to whom I have 

 referred should look through the telescope at once before I 

 had done so, so as to make the performance of the equatoreal 

 the more satisfactory. And there was the planet sure enough, 

 and, as luck would have it, very near the centre of the field. 

 I say luck as to this, because the instrument does not profess 

 to do so much, although I may say that if care be taken in the 

 adjustments, the object is always nearer to the centre than to 

 the edges of the field. I can assure the reader that on this fine 

 summer's day so successful an exhibition of the instrument 

 under such agreeable circumstances was a real treat to me ; 

 and I have no doubt that any enthusiastic amateur who may 

 happen to read this account will be able to imagine the satis- 

 faction I felt. As a still more severe test of the instrument, 

 but one which I did not quite like to risk first, I afterwards 

 found Arcturus in the same manner. As the power used 

 was only 20, and the diameter of the object-glass lj inch 

 only, there was a risk of not seeing stars, which, of course, 

 even first magnitudes, are extremely faint in broad daylight. 

 But if Venus be not found, it may always be taken for 

 granted that she is not in the field of view, unless, indeed 

 she is very near the sun, or the sky is at all hazy. Under a 

 clear atmosphere Jupiter can easily be seen also in broad 

 daylight, and Saturn when the daylight has only very slightly 

 declined. 



I have probably said enough to show that the portable 

 equatoreal is an instrument of a most recreative kind. But 

 it is more. It is really very useful. By means of it, for 

 iinstance, a comet whose e a. and n. p. d. are known may be 

 found very much earlier than with an ordinary telescope. The 

 instrument being set to a certain position, a comet may be seen 

 in strong twilight, when the chances would be greatly against 

 finding it by an instrument not graduated. At fhst view, it 

 may strike some readers as a very rough kind of thing not to 

 have circles graduated so as to be certain to a quarter of a 

 degree ; but two considerations will enable the reader to view 

 this in a very different light. The first is, that the circles gra- 

 duated are less than one inch in diameter and divided by hand 

 (of courso this would bo better done by machine) ; and 

 the second is, that the resultant error may bo the accumu- 

 lation of several errors in adjusting the instrument, all which 

 adjustments are necessarily rough. I will here remark, in answer 



