| Fuly 3, 1873] 
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NATURE 
181 
take the trouble to re-arrange them in some order more 
intelligible to the English reader than that of the alpha- 
betical sequence cf the common French names. 
LETTERS TO THE EDITOR 
[Tue Editor does not hold himself responsible for opinions expressed 
by his correspondents, No notice is taken of anonymous 
communications. ] 
Dr. Bastian’s Turnip-Cheese Experiments 
From Dr. Bastian’s letter in last week’s NATURE I learn that 
my last communication has afforded him satisfaction. The grati- 
fication which I feel at this expression of his approval is mixed 
with some surprise; for however confirmatory my experiments 
may be of his, so. far as relates to the bare fact that boiling is 
insufficient to destroy the germinating power of the turnip- 
cheese liquid, they certainly do not tell in favour of the inference 
which he is understood to draw from that fact. 
The experiments which’ Dr. Bastian was kind enough to show me 
last December were regarded by him as unequivocal instances of 
spontaneous generation. He will remember that at that time I 
stated to him, both orally and in writing, that the significance of 
the results in their relation to the doctrine of heterogenesis, 
appeared to me to be doubtful, and that I thought it probable 
that they would be interpreted by different persons in opposite 
senses, according to their preconceived opinions. I expressed 
myself in a similar manner at a discussion which took place 
on the subject last winter at the Royal Society. It was 
for the purpose of clearing up this doubt that I made the experi- 
ments recorded in my last communication. I did not expect to 
prove that the production of Bacteria in Dr. Bastian’s experi- 
ments was zof spontaneous, but merely to determine whether the 
fact afforded any support to the opposite conclusion. 
Having first shown that living organisms increase and multiply 
in the liquid in question, when boiled at the ordinary temperature, 
under circumstances which absolutely preclude the introduction 
of living matter from without, I prove that under otherwise 
similar conditions this result is not obtained when the liquid is 
subjected to ebullition at a slightly higher temperature. 1 show 
further that the liquideven when heated to 102°'5 C. suffers no 
impairment of its power of supporting the life of Bacteria, for by 
inoculating it with a drop of ordinary distilled water it at once 
becomes pregnant. Hence I conclude, not that spontaneous 
generation is impossible, but that the particular experiment in 
question is not an instance of it, and that no argument founded 
on it in favour of the doctrine is of the slightest value. 
Itis unnecessary for me to occupy your space by at any 
length adverting to the side questions raised by Dr. Bastian in 
the other paragraphs of his letter. 
In examining the liquids within a few days after heating 
rather than later, I followed his own method. 
I made no attempt to determine the temperature of ebullition 
in flasks with capillary orifices, because I know of no method by 
which it could be done accurately. Besides, it was not required 
for my purpose. 
I employed the word ‘‘chance” in its ordinary sense. In the 
sentence t2 which Dr. Bastian refers I explained that, although 
there may be a limit of temperature at which a liquid, before 
possessing the power of breeding Bacteria, is deprived of that 
power, experiments such as mine are insufficient to define that 
limit, As regards the turnip-cheese liquid it has been shown that 
between the temperatures of 100° and 102° C., the probability of 
pregnancy diminishes rapidly as the temperature increases. It is 
not as yet possible to say at what point the probability vanishes. 
University College, June 30 J. BURDON SANDERSCN 
The Zodiacal Light 
ConTRARY to Mr. Hall’s experience of astronomical books (see 
NATORE, vol. viii. p. 7), in neither Herschel’s *‘ Outlines of Astro- 
nomy,” Humboldt’s ‘‘ Cosmos,” nor Guillemin’s ‘* Heavens,” can 
I find any hint of a permanent difference between the brightness 
of the zodiacal light east of the sun and west ef it, though Arago’s 
** Popular Astronomy” says that according to Cassini, ‘‘it is 
generally less lively and less extended in the morning than in the 
evening.” But even if Cassini was correct, this is no positive 
proof of any difference between the two ‘‘branches” of the 
zodiacal light at the same time, seeing that he lived in the tem- 
perate zone, and probably did not observe it in both morning 
and evening at the same time of year. Mr. Hall’s situation in 
Jamaica is favourable for investigating this point, and I should 
not wonder if he finds the fact different from what he supposes. 
But even the books that consider the zodiacal light to surround 
the sun in the shape of a lens, acknowledge that it may extend 
further one way than another, and further at one time than 
another. T. W. BackuousE 
Sunderland, June 7 
AT about half-past one in the morning of June 5, the sky wa' 
clear, but the stars were not very brilliant, on account of the dif- 
fused light, and consequently the Eastern branch of the Zodiacal 
Light was very faint ; as I was endeavouring to trace its course, 
a strong beam of light appeared so suddenly as to have quite a 
startling effect ; it was not shot out like the rays of the Aurora 
Borealis, but gathered strength throughout its whole course, 
which lay through Aquarius, over the stars a and 6 Capricorni, 
through Sagittarius, across the Milky Way, and through Scorpio, 
passing to the N. of Antares; its visible length was therefore 
upwards of 100°, and as I was about to make accurate observa- 
tions, it suddenly disappeared, having lasted somewhat less than 
one minute. 
Its course was therefore nearly parallel to the Ecliptic, and 
about 6° to the N. of it; its breadth was from 3° to 4°; its 
brilliancy was equal to that of the brightest part of tae Milky 
Way, through which it passed, and therefore allowed me to 
judge very accurately ; and it had no colour. 
Now Humboldt says in his ‘‘ Cosmos,” * ‘* T have occasionally 
been astonished, in the tropical climates of South America, to 
observe the variable intensity of the Zodiacal Light,” and he 
considered the variation to be due to atmospheric changes, as I 
myself have hitherto done ; but in the case above no ordinary 
atmospheric changes could have produced the effect observed. 
It occurred June 4d. 18h. gom. Greenwich mean time, and it 
would be very interesting to know whether the magnetic instru- 
ments were affected at any part of the earth. 
Jamaica, June 1873 MAXWELL HALL 
Meteorological Influence of Trap Rocks 
THE thermometer in a mine, or coal-pit, rises, according to 
Herschel, 1° for every 90 feet of descent, or 58° per mile; and, 
according to Clerk Maxwell, the rate of increase in this country 
is 1° for every 50 feet of descent. These results are obtained in 
passing through a very small portion of the superficial crust of 
the earth ; such, for example, asa part of the coal formation, 
which possesses.a very low degree of conductivity. We can 
hardly, indeed, conceive a worse conductor thana crust consisting 
of alternating strata of freestone, shale, till, coal, limestone, &c. 
But these strata are very frequently perforated by comparatively 
homogeneous intrusions in the form of trap dykes, which not 
only possess greater conductivity, but which, from the analogy 
presented by volcanoes, \ery probably extend down to the molten 
matter subjacent to the external crust of the earth. Such trap 
dykes may be compared to an iron poker thrust through the super- 
ficial strata having its lower end ina state of fusion, and its upper 
end kept cool by radiation into the atmosphere. Through any 
continuous dyke, if this view be correct, there will therefore be a 
more rapid escape of heat ; and when such igneous rocks occupy 
spaces of many square miles of the earth’s surface, one would, 
at first sight, expect them to play a very important part in affect- 
ing the meteorological conditions of the district in which they 
are found. They might be expected, by the large amount of heat 
which they conducted freely to the earth’s surface, to stimulate 
the growth of plants ; and by the radiation of the liberated heat 
into the atmosphere, they ought to become—especially during 
night—the generators of storms, by causing a constant ascent of 
rarefied air. It is quite true, however, that the meteorological 
effects of such an agent must, as in the case of volcanoes, be 
observed by the far grander cycle of disturbances initiated by the 
solar heat ; and that its agricultural efficiency may be, to a large 
exteat, negatived by differences of chemical constitution, acidity, 
and exposure, Still, however, the influence is there, and ought, 
in one way or other, to make itself sensible. ; 
Do any of your readers possess information bearing upon this 
question? Such, for example, as experiments on the con- 
ductivity of the different kinds of trap as compared with the 
stratified rocks, or observations of the temperature of the air, 
especially during nizht, above trap-rocks as compared with that 
* Otte’s transl., vol. i, p. x32, 
