+496 PROFESSOR PIAZZI SMYTH ON THE 
are so very meagre and obscure, that they require all the knowledge of the phe- 
nomenon acquired up to the present day, to be applied to make them mean 
anything. Marran, with whose theory Kxpier’s fancy seems to agree, when 
discussing, in 1754, the history of the phenomenon, gives the German full credit ; 
but Humpotpt, in 1844, with different theoretical views, dismisses the case of 
his countryman in a very summary way. 
An earlier claim still has been brought forward, on account of the mention, 
in'a letter from RorHMann to Tycno Braue, that in the spring the twilight 
ceased not till the sun was 24° below the horizon; and as the true twilight would 
have ceased long before the sun was so low,—it is contended that RorHmMann 
must have seen the zodiacal light, though without remarking anything peculiar 
in it, or different from the ordinary course of the evening. 
So that the first satisfactory and clear description is still that of CHInpREY in 
1661, already alluded to. ‘‘ There is another thing,” says he, in his Britannia 
Baconica, p. 183, “ which I recommend to the observation of mathematical men; 
which is, that in February, and for a little before and after that month (as I have 
observed for several years together), about six in the evening, when the twilight 
hath almost deserted the horizon, you shall see a plainly discernible way of the 
twilight, striking up towards the Pleiades, and seeming almost to touch them. It © 
is so observed any clear night, but it is best a/c nocte. There is no such way to 
be observed at any other time of the year. But what the cause of it in nature 
should be, I cannot yet imagine, but leave it to further inquiry.” 
Here, then, is a clear and simple account of one phase of the phenomenon, 
marking it as a something unusual, as different from ordinary twilight, as con- 
stant in that anomalous difference, and therefore well worthy of being carefully 
inquired into. 
In his Travels in Persia in 1668,* Cuarpin mentions having seen the tail of 
the great comet of that year above the western horizon after sunset; the head 
being visible only in the southern hemisphere. Cassini and Marran, writing some 
years after, under the influence of the then new discovery of the zodiacal light, 
asserted that it must have been this which Cuarpin saw; and he is even made 
out by DELAmsre to have been the original discoverer of it. The comet of 1668 
having, however, appeared again in 1843 (that is, they are supposed, with the 
greatest probability, to be identical; and if not identical, still they are at least 
both specimens of the comet genus), has given us the opportunity of determining 
whether Crarpiy’s description applies to the zodiacal light or to the comet, which 
though so very unlike each other, were not only confounded at the former appa- 
rition, but at the latter also; when the tail, as before, was the only part visible 
in the northern hemisphere. The slightest glance at the accompanying drawings 
* Edit. de Langles, t. iv., p. 326; and t. x., p. 97. 
a a iit 
