518 PHILOSOPHICAL TRANSACTIONS. [ANNO 1784. 



ing how near one can come to the truth in this way : and though neither the 

 right ascensions nor the declinations are laid down by it, nor the distances be- 

 tween the stars measured ; yet their apparent situations being preserved in black 

 and white, with the day and year, and hour if thought necessary, written under- 

 neath, each card becomes a register of the then appearance of that small portion 

 of the heavens ; which is easily re-examined at any time with little more than a 

 transient view ; and which yet will show on the first glance, if there should have 

 happened in it any variation of consequence. It is obvious however that very de- 

 licate observations are not to be made in this way. 



My design was, after marking down all such stars as are visible with so small 

 a magnifier, to go over the whole again with another telescope of a higher power, 

 divided in the same way ; and after that, with a 3d and 4th ; so as to compre- 

 hend every star I could discern. That would discover smaller changes : but it 

 must be a work of time, if attempted at all. After such a rough map of the con- 

 stellation is made, the endeavouring to ascertain the right ascensions and declina- 

 tions of these, may perhaps be adviseable in the next place, rather than searching 

 for more. 



In observing in this way, it is manifest that the places of such stars as happen 

 to be under or very near any one of the wires, must be more to be depended on, 

 than of what are in the intermediate spaces, especially if towards the edges of the 

 field : so also what are nearest to the centre, because better defined, and more 

 within the reach of one wire or another. For this reason, different stars in the 

 same set must successively be made central, or brought towards one of the wires, 

 where any suspicion arises of a mistake, in order to approach nearer to a cer- 

 tainty : but if the stand of the telescope be tolerably well adjusted and fixed in its 

 place, that is soon done. This then is the method I would recommend to the 

 practical astronomer, for becoming acquainted with the appearance of the stars, 

 and setting a watch over the heavenly motions. After a very few trials, every 

 one would find this easy. And if each person of every rank among astronomers 

 would take a constellation or two under his care, the numbers who could under- 

 take it in this way would compensate for the defects of a plan which cannot aspire 

 at great accuracy. The labour of it, even at first, is but little. 



Before concluding this head, I shall add a few hints. Whether this method 

 be followed, or any other, if a general plan be set on foot, whoever undertakes a 

 constellation, or district, should determine to examine it with as great accuracy 

 as he can ; yet never be ashamed to let others know of his mistakes. The error 

 of one proves a caution to another. Such a rough sketch, once made, will be 

 found of great use in knowing which star next to examine with greater care. He 

 who can do no more than this, will do a useful work by going thus far : and his 

 frequently sweeping over his district in this way, may lead him to a discovery 



