A pril 6, 1882] 
NATURE 
543 
dition, and that a crowding of such luminous matter involves an | fras, tree ferns, and myrtles ; and (4) the interior }lains repre- 
increase of luminosity, may we not infer with a high degree of 
probability that the striz: are themselves aggregations of matter, | 
and that the dark spaces between them are comparatively 
vacuous, 
It is true that such a view of the case would seem to imply 
that, in gaseous media, the better the vacuum the more easily 
can the electricity pass; and that this might at first sight appear 
to be at variance with the known fact that the resistance of a 
tube decreases with the pressure until a minimum, determinate 
for each kind of gas, and then increases. Bnt it has been sug- 
gested by Edlund (Aznales de Chemie et de Physique, 1881, tom. 
iii. p. 199) that the resistance of a tube may really consist of 
two parts, first, that due to the pa-sage of the electricity through 
the gas itself, and, secondly, th t due to its passage from the 
terminals to the gas; and also that the former decreases, while 
the latter increases, as the pressure is lowered. On this suppo- 
sition, the observed phenomena may be explained, without 
assigning any limt to the facility with which electricity may 
_ traverse the most vacuous space. 
We may even carry the suggestion of a resistance of the second 
kind a little further, and suppose that there is a resistance due 
to the passage of electricity from a medium of one density to 
that of another, or from layer to layer of different degrees of 
}ressure, And from this point of view, we may regard the striz 
as expressions of resistance due to the varying pressure in dif- 
ferent parts of the tube. Into the question, whence this varia- 
tion of pressure, I am not at present prepared to enter; it must 
suffice for this evening, to have shown that the conclusions 
which we have drawn from our experiments, are not in dis- 
accordance with other known phenomena of the electrical 
discharge. 
The warning hand of time bids me not to prolong my discus- 
sion of the subject. But before closing, I would point out that 
these laboratury experiments are not unsuggestive in reference 
to larger questions. It has long been, and still is, a disputed 
question whether a display of the aurora borealis ever takes 
place at any consideratle elevation above the earth’s surface. 
On the one hand, ob-ervations are cited giving a not unfrequent 
elevation of nearly 200 miles; while on the oth2r, experiments 
with vacuum tubes appear to limit the range to less than forty 
miles. The observation is perhaps a doubtful one at best ; it is 
not easy to fix the position of so faint and flickering a pheno 
menon, and it is perhaps even more difficult to identify a parti- 
cular phase of it when seen from two distant positions. But the 
recorded data are still entitled to some consideration, especially 
if it has been shown that the evidence furnished by vacuum tubes 
is not conclusive against the higher estimate. 
It would be very pleasant, if, wafted by the breezes of scien- 
tific imagination, we weve to set full sail, and navigate our bark 
into still more distant space. And, indeed, we are under no 
slight obligations to those strong minds and courageous spirits 
who thus adventure themselves out beyond well-known waters ; 
for the treasures which they bring back from every such voyage 
are both valuable and strange, and they set men thinking on 
new and untrodden Ines. but lest, less fortunate than my 
neighbours in any such venture, I should fail to fall in witha 
returning current, capable of recovering my expended energy, 
and of restoring myself to ¢erva firma, | must here pause. It 
is, however, said, that in the mind of every one, even the most 
philosophic, there is a tender part ; and therefore I must ask 
your indulgence, if, while resolutely turning my back on physical 
speculations, I still return for a moment to my first love, mathe- 
matical contemplation. For, in the region which we have been 
considering, namely, the magnetic field, explored and represented 
by its electric action, we seem to have entered upon a world which 
Riemann might have longed to see, a world wherein Lobatcheff- 
ski and Beltrami might have enjoyed the full fruition of realised 
ideas, and where even Clifford might have found abundant scope 
for the exercise of his inexhaustible powers of imagination and 
of thought. 
FLORA OF NEW SOUTH WALES IN ITS 
GEOLOGICAL ASPECT 
THs, the oldest of the Australian settlements, may have its 
area grouped as follows :—(1) That of the sandstones or 
poor country represented by the Proteads and Epacrids ; (2) the 
eastern slopes of coast range represented by the tree-nettles and 
the palms ; (3) the cold mountain shrubs re re ented by sassa- 
sented by Chenopods and Composite. It may be wondered 
how the distribution of the vegetation has originated. ‘That the 
Australian continent has risen slowly, is gathered from numerous 
proofs, among others the very apparent one of the strata exhibit- 
ing preponderately a horizontal plane, It may further be inferred 
that in its uplifting, the outer rim of the continent was slightly 
more elevated than the interior, This taken into consideration 
along with what doubtless at one time existed, namely, a great 
inland sea, abundance of marshes and mud, and a once probable 
greater rainfall, and particularly the latter, though one and all 
may have contributed to the present physical features, and con- 
sequently plant life. Another interrogatory arises, viz. Whence 
the coal-seams? As to these, there is some likelihood they are 
the remains of vegetation borne hence from a now sunken conti- 
nent eastward of Australia ; New Zealand, Norfolk, and Howes 
Island being outliers or now mere island vestiges of the said 
great land area in the Pacific Ocean. 
Of the four local divisions above enumerated, the most typical 
vegetation of the fir t is the group Proteacex, a very ancient 
family, extending back to the secondary period of geology, from 
which time Australia apparently has never been submerged. A 
point of very considerable importance as bearing on this long- 
continued stability of the Australian continent may be derived 
from the remarkable close relationship and insensible gradation 
of some plants ; for instance there is great difficulty in separating 
species of Eucalypti, Banksias, &c. Thus it may be said none 
or few of the connecting links have been lost, as must necessarily 
have been the case had submergence and elevation of the land 
have occurred. 
Many curious problems yet await investigation, such as the 
fertilisation of the Proteads, including the Styleworts and 
Goodenia family. Again, have the Epacrids once been a 
family of trees, wherefrom the living species are but decadent 
examples? The Casuarinez, or Beefwod tribe, are undoubtedly 
an ancient group, and like conifers, flourished in the dawn 
of life. The second division of the eastern sl»pes, Palms, and 
Tree-nettles possibly may have had an Asiatic origin, through 
the Malayan Archipelago. They appear not to be truly 
Australian in origin, but themselves only long established 
cclonists. On the contrary, among the third divi-ion of the 
cold mountain scrub-:, the Dorophoree (Sassafras) hold a con- 
spicuous place, and evidently are of Australian derivation. The 
peculiar vegetation of the interior plains or fourth division, the 
Chenopods and the Compositz, are rapidly becoming one of the 
past, and the small species even now are sensibly giving place 
to the introduced grasses and weeds. Apart from the groups 
mentioned as most typical of the four areal divisions in question, 
as regards the Acacias and Eucalypts, they have the widest dis- 
tribution and complicated genera, They both appear to be 
genera at their zenith, having existed long enough to pass into 
redundant forms, but not long enough to have been exposed to 
vicissitudes and decline. Their absence from Howe's Island 
and New Zealand shows they in all likelihood did not belong 
to the hypothetical submerged continent, nor: are they old 
enough to be found along with the laurel and other remains of 
the gold drifr. (Abstract of a communication by Mr. Robert 
Fitzgerald, F.L.S., read at the meeting of the Linnean Society, 
February 2, 1882.) 
UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE 
CAMBRIDGE.—The recent report of the Council of the Senate 
relative to the proposed Prosessorship of Animal Morphology, is 
creditable both to the University and to the Council. We think - 
it desirable to quote some of its paragraphs entire. ‘‘ The suc- 
cessful and rapid development of biological teaching in Cam- 
bridge, so honourable to the reputation of the University, has 
been formally brought to the notice of the Council. It appears 
that the classes are now so large that the accommodation pro- 
vided but a few years ago has already become insufficient, and 
that plans for extending it are nuw oc.upying the attention of 
the Museums and Lecture-Rooms Syndicate, 
‘©It is well known thai one branch of this teaching, viz., that 
of Animal Morphology, has been created in Cambridge by the 
efforts of Mr. F. M. Balfour, and tka! it has grown toits present 
importance through his abili:y as a teacher and his scientific 
reputation. 
‘« The service to the interests of natural science thus rendered 
