on the local arrangement of the celestial bodies in space. 317 
i-£ of its light is also of an equal lustre with Procyon, which 
consequently, with regard to Sirius, is of the 1^ order; then, 
by compounding, it follows that Capella to Sirius is a star of 
the \\ order, and from this we obtain the following series. 
Sirius 1, Capella 1%, Procyon 1 J, /3 Tauri 3, < Auriga? 6, H Ge- 
minorum 12, and d Geminorum 15. By this connection we 
shall be able to obtain an equalisation of the same ultimate 
star with all the standards ; for if Sirius must be removed to 
the 15th order, to appear as faint as d Geminorum ; and if 
Capella, and also a. Lyras must be removed to the 10th order 
of distances to appear as faint as the same star, then any star 
of the size and brightness of Sirius, Capella, and a. Lyras 
must generally appear as faint as d Geminorum, when it is 
removed to nearly 12 times its distance; and the more stars 
of the first order are admitted in these general equalisations 
reduced to the same faint star, the more will the probability 
of the result be extended. Now as d Geminorum is a star 
of the 6th magnitude, we may expect that a still fainter visi- 
ble star will give a somewhat greater extent to the reach of 
the natural eye, if however I take its vision, including other 
stars of the 1st magnitude, to extend to the 12th order of dis- 
tances, there will probably be no material error, at least 
none but what a diligent astronomer, who is provided with 
the necessary apparatus, may correct by observation. 
But the extent of natural vision is not limited to the light 
of solitary stars only ; the united lustre of a number of them 
will become visible when the stars themselves cannot be 
seen. For instance, the miiky way ; the bright spot in the 
sword handle of Perseus ; the cluster north of vj and H Gemi- 
norum; the cluster south of Fl. 6 and 9 Aquilae; the clus- 
