Fan. 12, 1882]. 
LETTERS TO THE EDITOR 
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A Glimpse through the Corridors of Time 
In a letter which appeared in last week’s NATURE (p. 217), 
Dr. Dupré refers to a ‘‘ too much forgotten paper by Immanuel 
Kant,” and speaks of Kant’s contributions to natural science as 
_ being, at present, ‘‘almost universally overlooked.” 
Whatever may be the case elsewhere, I do not think that, in 
England, we are open to this reproach, inasmuch as in the year 
1869, when I had the honour to be President of the Geological 
Society, a very considerable portion of my anniversary address 
*©On Geological Reform” was devoted to an attempt to do 
justice to Kant’s work, and to indicate the high place which it 
occupies in the history of scientific geology. The address is re- 
printed in my ‘‘ Lay Sermons,” and therefore I have reason to 
know that a considerable proportion of the reading, or at any 
rate book-buying, public has no excuse for ‘‘ ov2rlooking Kant’s 
work,” 
I may remark, in passing, that, so far as my knowledge 
extends, the extreme ‘‘ Uniformitarianism” which Prof. Ball 
attacks, has long been as much ‘‘a creed outworn” as “ Plu- 
tonism ” or ‘‘ Neptunism.” Indeed, I said as much in 1869, 
T. H. HuXLey 
Normal School of Science and Royal School of Mines, 
South Kensington, January § 
Outburst of Sun-Spots, July 25, 1881 
My letter of August 5, 1881, which appeared in NaTuRE, 
vol, xxiy. p. 508, stated that a considerable group of sun-spots 
burst into appearance between 4 and 5 p.m. (about) on July 25, 
1881 ; or more exactly that-the new group was absent at 3h. 
58m. (z.¢c. in negative No. 1175), but was present at 4h. 47m. (2.e. 
in negative 1176), local apparent time ; further, that no addi- 
tional negatives could be taken here until July 30, when the 
spots had disappeared. 
This communication has elicited obliging notices by other 
observers, including Prof. Piazzi Smyth and Prof. Perry, F.R.S., 
in NATURE, besides others posted to me direct. The observers 
were not able to observe the sun when the outburst occurred, 
nor for some twenty-two hours afterwards ; none of the observers 
saw the new group. 
One of the observers remarks: ‘‘ I fancy your sudden group of 
spots is after all a curious system of blemishes in the negative ! ” 
Certainly the appearance of the negative (No. 1176) did not (to 
me) admit of conjectures suggesting the wreality of the spots, 
However, in presence of the remark now offered, I made 
inquiries of the photographer, Mr. L. H. Clarke, as to the cir- 
cumstances connected with his detection of the outburst. I inclose 
his narrative (see below). It establishes the fact that he frst saw the 
new spot-group ov the ground-glass slide used for focussing the 
photoheliograph, and indeed that it was ‘his view of the unex- 
pected event which urged him to persevere (notwithstanding the 
clouded state of the sky) in securing a negative, z.c. No. 1176, 
on which the new spot-group he had seen on the ground glass 
slide stands photographed. His narrative further establishes 
narrower limits of time in which the outburst occurred, 7.e. 
between 3h. 58m. to about 4h. 35m., instead of to 4h. 
47m. p.m. 
I communicate the foregoing facts, as they are essential 
circumstances of the event, and should be placed on record. 
J. B. N. HENNESSEY 
Dehra Doon, N. W. Provinces, India, December 16, 1881 
On July 25, 1881, the sun was quite invisible owing to clouds, 
until towards 4 p.m., when a temporary break occurred, and I 
took negative No. 1175 at 3h. 58m. p.m. After this the sun 
NATURE 
241 
again became invisible, while the rising clouds were so dense as 
to present little hore of getting another negative ; so, as evening 
was approaching I was thinking of closing work for the day, 
when, while I was still watching at the instrument, an un- 
expected opening occurred in the rising clouds below the sun, 
and, soon after, the sun’s image appeared on the ground glass 
used for focussing. To my surprise I now saw, at about 4h. 
35m. p.m., a large group of spots about the sun’s centre, which 
were quite absent in the previous negative, No. 1175; little 
expecting anything of the kind, or indeed to see the sun at all 
that evening, I was not ready to expose a plate, but now seeing 
what had happened, I determined to persevere, though the 
clouds were very unpromising of another break. So I at once 
took points on my blue setting glass, as is usual to set the instru- 
ment by (so as to avoid needless hiding of spots behind the 
wires), and having done this, I prepared a plate as. quickly as 
possible, and set the exposing slide all ready, though the sun 
now was invisible ; fortunately another opening occurred at 4h. 
47m. p.m., when I took negative number 1176, in which appears 
the group of new spots atout the sun’s centre, which new group 
I saw without doubt at about 4h. 35m. on the ground glass for fo- 
cussing. I then continued to watch for another negative until 
5h. 30m. p.m., when the sky having become quite dark, I gave 
up work for the day. L. H, CLARKE 
December 2 
Polymorphism of the Flower-heads of Centaurea Jacea 
In Centaurea Facea, the flower-heads of the same stem, as far 
as I have seen, are always of the same form, but different stems 
of the same locality often present astonishing difference in their 
flower-heads. 
In the most common and apparently original form the flower- 
heads consist of florets which are all of the same tubular shape 
and all contain both fully developed anthers and stigma, the 
divergence of the outer florets giving to the whole head a 
diameter of 20-30 mm. (see H. Miiller, ‘‘ Bie Befruchtung der 
Blumen,” p. 382-384). From this original form variation has 
gone on in two opposite directions, the final effects of this varia- 
tion being on the one side most conspieuous male flower-heads 
of 50-55 mm. diameter, and on the other side less conspicuous 
female flower-heads of 30-35 mm. diameter. In both these 
extreme forms the outer row of florets possesses greatly enlarged 
radiating corollas which are sexually functionless, but useful in 
making the flower-mass more conspicuous. In the male flower- 
heads anthers and pistils of the disk-flowers are well-developed, 
but the style-branches never open so as to expose their stig- 
matic surfaces, and in their basal portion are grown together: 
In the female flower-heads, on the contrary, only the pistil of 
the disk-flowers is fully developed, the anthers being pollenless, 
shrivelled, and brownish-coloured. 
These two extreme forms are linked with the original one by 2 
continuous series of gradations. When in the original form 
variation begins in the one direction, the outer row of florets 
gradually becomes longer and more radiating, and in the same 
degree their sexual organs diminish in size and become funct'on- 
less, the anthers first aborting, and then the pistil. Finally, the 
barren ray-florets continuing to increace, the pistils of the disk- 
florets, too, become functionless, and the conspicuous male 
flower-head is accomplished. 
In the contrary variation some of the outer florets of the 
original form begin to diminish in size, while their anthers 
become brownish and pollenless, and this change step by step. 
proceeds inwards and seizes a greater and greater number of 
disk-florets, until the whole flower-head is female, and rednced 
to a diameter of 15-18 mm. This state being reached, the 
corollas of the marginal flowers recommence to increase and 
become radiating, while in the same time their anthers disappear 
without leaving any trace, and their style-branches remain closing 
together. 
These are, shortly sketched, the main varieties of Centaurea 
Facea, near Lippstadt. Further details are about to be pub- 
lished in one of the next numbers of Kosmos. 
Lippstadt HERMANN MULLER 
The Weather 
THIS morning I noticed the first blossoms of the Colt:foot 
(Tussilago farfara), ordinarily considered an indication of the 
near approach of spring: For many~ years a generous rivalry 
has existed between myself and a friend (both travellers on the 
