1 o 
Dr. Herschel's Observations on 
M. Cassini, I cannot decide whether the black list which he 
saw was the same which I have observed, M. de la Lande 
says ( Ast . Vol. III. page 441.) that Cassini saw it divided by a 
small black line into two equal parts. M. de la Place ( Memoire 
sur la Theorie de I’Anneau de Saturne ) mentions that Cassini 
saw the breadth of the ring divided into two parts almost 
equal. It should seem from this, that M. Cassini was not par- 
ticularly attentive to the proportions of the division ; in which 
case his observations and mine will agree perfectly well ; but 
if he has any where expressly mentioned, that the ring was 
divided into equal parts, so that we may be certain he was 
particularly attentive to that circumstance, it will follow evi- 
dently that the ring, since his time, has undergone a very ca- 
pital change in its construction. 
Mr. Short assured M. de la Lande, that he had seen many 
divisions upon the ring, with his telescope of 12-feet. A thing 
of such consequence, and so new, ought certainly to have been 
given in a more satisfactory and circumstantial way than only 
by communicating it, from memory, in conversation, to an- 
other person. Besides, it is well known that many telescopes 
will give double and treble images, and that especially those 
which have large apertures are subject to tremors, which mul- 
tiply small lines. For these reasons, we can hardly take into 
account observations that seem not to be sufficiently established. 
What has been said is, however, by no means intended to un- 
dervalue Mr. Short's observations; and this, I hope, will be 
evident, when it is remembered how scrupulously I have just 
before set aside four of my own, because I looked upon them 
as not sufficiently confirmed. 
Mr. Hadley's observation of the division of the ring, with a 
