[ 2 '3 1 
XII. On the Conjlrutllon of the Heavens . 
By William Herfchel, Efq. F. R. S- 
Read February 3, 1785.. 
T HE fubjedt of the ConftruCtion of the Heavens, on 
which I have fo lately ventured to deliver my thoughts 
to this Society, is of fo extenfive and important a nature, that 
we cannot exert too much attention in our endeavours to throw 
all poffible light upon it; I fhall, .therefore, now attempt 
to purfue the delineations of which a faint outline was begun 
in my former paper. 
By continuing to obferve the heavens with my lad: con- 
drudted, and fince that time much improved indrument, I am 
now enabled to bring more confirmation to feveral parts that 
were before but weakly fupported, and alfo to offer a few hill 
further extended hints, fuch as they prefent themfeives to mv 
prefen t view. But fird let me mention that, if we would 
hope to make any 5 progrefs -in an inveftigation of this delicate 
nature, we ought to avoid two oppofite extremes, of which I 
can hardly fay which is the mod: dangerous. If we indulge a 
fanciful imagination and build worlds of our own, we mud: 
not wonder at our going wide from the path pf truth and 
nature ; but thefe will vanifh like the Cartefian vortices, that 
foon gave way when better theories were offered. On the other 
hand, if we add obfervatio'n to obfervafion, without attempt- 
ing to draw not only certain concludons, but alfo conjectural 
views 
