334 Scientific Intelligence. 
the light of comets, which is greatly influenced by their positions rela- 
tively to their perihelia. 
It is probable that at least the head of the comet was much brighter at 
the middle of June than it was after the 1st of July, and we shall wait 
with much interest for accounts of it from southern observatories, espe- 
cially from the Cape of Good Hope, which has often, in similar emer- 
gencies, proved itself the most important astronomical position occupied 
by any existing observatory. | . 
From the above elements, the diameter of the nueleus may be variously 
estimated at from 150 to 300 or 400 miles. On July 2d the breadth of. 
the head at the nucleus was 156,000 miles, the height of the inner enve- 
lope 11,500 miles, and the length of the tail about 15,000,000 miles. 
The comet was seen between one and two o’clock on Sunday morning, 
June 30th, by Dr Brunnow, at the Observatory of Ann Arbor. This is 
the earliest authentic account of its visibility which has come to my notice. 
The head could not have been seen on Friday evening, although observa- 
tions to that effect have been reported. ‘The extremity of the tail, how- 
ever, must have been within view for some time previous, though too 
faint to attract notice. " 
The reports current of the identity of the comet with those of 1264 and 
1556 are without any foundation. (From the advanced sheets of ‘ Silli- 
man’s Journal” for September 1861.) 
The Livingstone Expedition. 
Kineare Mourn, ZamBezi, 
21st January 1861. 
My pear Mr Youne,—The discovery we have made of abundance ot 
coal existing on the Zambezi above Kelvabassa.will be of importance 
some day, when the obstacles thrown in the way of civilisation by the 
Portuguese have been removed. The first coal-field is that at Chicova, 
just where the river becomes narrowed by the hills; it is to be seen when 
the river is low, being then disclosed in the bed on the: north side ; it 
seems of good quality—burns freely without requiring a furnace. Strange 
the people seem to have no name for it. It has been broken up by trap- 
rock being forced in among it; but I have no doubt it may be had nearer 
the surface through the whole of the Chicova plain. The next seam is 
that near “‘ Mangenene Hill,” where it crops out on the face of the rock 
on the south of the river. On the north we found coal and shale in the 
bed of a stream coming from the hills, but failed to reach the seam itself; 
but we found pipe-clay which had undergone the action of fire. Pipe-clay 
is very common in the country. 
Again, in the country beyond the Kafue, there is abundant evidence of 
coal at the foot of the hills to the north, and in the Batoka country, | 
where we left the Zambezi. As we ascended the River Zangue, we came 
to beds of alum slate, covered with an efflorescence of the salt, under 
this was shale and coal containing large stems of vegetables, which seemed 
like Stigmarias; but I was unable to gather fossils, showing anything 
definite. From the sections we saw in that ascent, I was quite satisfied 
that the schist rocks of this country are modifications of the sandstone and 
slates altered by heat, and tilted up by the igneous rocks of granite, 
syenite, and massive quartz, which have been injected. The latest change 
has been the eruption of trap; but this seldom changes the position of 
other rocks. It has been forced through holes and between strata, but 
seems not to have possessed sufficient heat to render the rocks plastic. To 
this belongs the change which has caused the great Victoria Falls, the 
