Oct. 21, 1886 | 
NATURE 
595 
Fe,O,, but at the same time a base is formed, the compounds 
of which are totally different from those of the ferrous oxide, 
but which resemble in their chemical properties the salts of 
alumina, Al,O3, with which they are isomorphous. Here there 
is evidently a change, not merely of composition, but of con- 
stitution ; the addition of oxygen has not only altered the rela- 
tive weight of the constituents, but has completely changed the 
structure of the molecule in a definite direction, and impressed 
on it a constitution analogous to that of the molecule, Al,O;, 
with which it is isomorphous. Now, when I had shown that 
this change in the constitution of the salts of iron was attended 
by a marked change in their physiological action, when I 
had proved that the physiological action’ of the ferrous salts 
was analogous to that of the salts of the other members of the 
magnesian group, which they resemble in chemical constitution, 
and that the physiological action of the ferric salts was analogous 
to that of the salts of alumina with which they are iso- 
morphous, and when it was proved that an analogous con- 
nection existed between the chemical constitution and physio- 
logical action of the compounds of the elements of all the more 
important isomorphous groups, I think nothing but a complete 
misapprehension of the meaning of the terms chemical constitu- 
tion and isomorphism could have led Dr. Brunton to allude to 
my researches as an ‘‘atéempt to show that a connection exists 
between the form in which various bodies crystallise and the 
mode in which they act on an animal body.” The same error 
as regards the meaning of the term chemical constitution has led 
Dr. Brunton to fail to comprehend the bearing of the experi- 
ments of Crum Brown and Fraser on the question, on which, 
in fact, they throw no light, although evidently regarded by him 
as a beacon for subsequent observers. These gentlemen found 
that by the addition of an ethyl or methyl molecule to strychnia 
its physiological action was profoundly modified, and concluded 
that this was owing to the chemical constitution of the substance 
being changed. As they worked with a reagent, strychnine, of the 
chemical constitution of which we are still ignorant, it was im- 
possible for them to know if the addition of an ethyl or methyl 
group had made any change in its chemical constitution. The 
probabilities are that no such change had taken place, as the 
new compounds were addition and not substitution compounds. 
It is not merely for asserting a claim to priority that I make this 
communication, although I think seu cuigue a very good rule ; 
but I wish to point out the causes which in my opinion are not 
only retarding the progress of physiology in this direction, but 
which are tending to throw it back to where it was before the 
publication of my earlier experiments nearly fifty years ago. 
October 6 JAMES BLAKE 
Relation of Coal-Dust to Explosions in Coal-Mines 
If is a stubborn and grievous fact that the loss of life by 
explosions in coal-mines has risen in the last decade, although 
the number of explosions has fallen. This points clearly to some 
essential defect in the remedies adopted. The remedies in use 
apply apparently to one class of explosions only, hence the de- 
crease in the number of explosions. But, unhappily, there are 
many to which they do not apply, and those the worst ; hence the 
larger number of lives lost. Some research, which has much 
engaged me of late, and which I hope soon to make public, has 
led to the conclusion that possibly the reason of this is about to 
be, or is even already, detected. 
Many, well competent to judge, have thought that too much 
attention has been given to gas, and too little to dust. This is 
a growing conviction, both in Germany and in England, and of 
late years the dust has had considerable attention. A work, 
recently published (September 1886) by Messrs. W. N. and J. 
B. Atkinson (Government Inspectors of Mines), entitled ‘* Ex- 
plosions in Coal-Mines,” strives, and I think fully succeeds in 
establishing that many of the most disastrous colliery explosions 
in the last six years have been practically ‘‘ dust explosions,” 
My conclusion, from certain simple physical and chemical ex- 
periments, and from a most careful microscopic examination of 
coal-dust from various seams worked in this field, is that the 
Messrs, Atkinsons’ view is right, and, moreover, that the atten- 
tion hitherto given to coal-dust has not only been useless, but 
absolutely pernicious, since it las lulled into a state of false 
security. 
I have been down several typical coal-pits in this district (the 
Durham field), such as Seaham, Murton, Silksworth, Pelton, 
&c., and in some of them I have seen the water-pipes along 
stop-cocks, and have found the dust on such roads so damp as to 
be rendered harmless, if it had not been so already, but the fine 
dust which coats the upper faces of the roof-timbers was there 
untouched, lying often to the depth of half an inch. Now, the 
bottom dust, as we may call the former, I am prepared to prove 
is almost if not quite universally harmless; and the per dust, 
as we may call the latter, I am equally prepared to prove is in 
the vighest degree dangerous, and especially a certain por- 
tion of it, which I propose to call ‘‘focculent dust.” Lastly, 
I claim to be able to establish that the main source of 
the really dangerous dust is that portion of the coal called 
variously ‘‘ dant,” ‘‘mother of coal,” and ‘‘ mineral charcoal.” 
The upper, and especially the flocculent dust, possesses physical 
and chemical properties wanting, or existing in the most 
shadowy form, in the bottom dust; and the microscopical 
aspect emphasises these differences, as well as shows the rela- 
tion of the former to what is very appropriately called ‘‘ mineral 
charcoal.” 
It would pass beyond the limits of a letter to enter into parti- 
culars, but the observations and opinions of others may be 
hereby evoked, and this good work of saving life and property 
be materially furthered by your kindly admission of this letter to 
your pages. I will now only add that this ordinary upper dust 
and this flocculent dust removed, or rendered innocuous, it is 
my firm conviction that the number of explosions will rapidly 
fall, and also the loss of life be greatly reduced. This is the 
goal of my effort. Some practical men may indicate means, 
and perhaps I, who am a student, may be permitted to suggest 
that keeping the ventilating air-current saturated with aqueous 
vapour, rather than direct watering, would, if it be practicable, 
both lessen the amount of this dangerous dust, and also facilitate 
its removal. ARTHUR WATTS 
Bede College, Durham, October 12 
Volcanic Ash from New Zealand 
A SAMPLE of the ash ejected during the recent eruption in 
New Zealand has just reached me through the kindness of Mr. 
W. Ferguson, Harbour Engineer, Wellington. It was collected 
sixty miles from the seat of the volcano. 
The ash is of a gray colour, of a somewhat darker shade than 
that from Krakatdo. The dark-coloured constituents of the 
New Zealand ash consist principally of black scoriaceous frag- 
ments and ferruginous particles of indefinite character ; those of 
Krakatao consist mainly of magnetite and hypersthene, well 
defined. The following minerals are contained in the New 
Zealand ash :-— 
Flagioclase Feldspar, very fragmentary, limpid, showing poly- 
synthetic striations in the polariscope, and sometimes medial 
twinning line. The few well-formed cry:tals observed recall 
the tabular forms from Krakatao (described in my paper, Proc. 
Roy. Dublin Soc., vol. iv. p. 291). There is a notable absence 
of the cellular vesicular covering observed in the Krakatdo feld- 
spar, and so sugge tive of the pulverisation of a ready-formed 
pumice. 
Hornblende, in elongated prisms, sometimes fibrous longi- 
tudinally or striated ; colour dark green, pleochroic green longi- 
tudinally to brown ; extinction makes a small angle, less than 
15°, with the prism axis; occurs occasionally included in the 
feldspars. It is scarce. 
Biotite and a golden-coloured mica are common in well- 
formed crystals of hexagonal outline, remaining dark between 
crossed Nicols. 
Tryon Pyrites, free and in embedded grains; striated pale 
yellow octahedral forms. Scarce. 
Magnetite, in lustrous black octahedral forms. Not abundant. 
Sulphur, in small broken pale-yellow fragmerts ; burns with 
the characteristic smell, held over a lamp, Scarce. 
Glass, remaining dark between crossed Nicols; variously 
coloured and often containing crystallites arranged fluxionally. 
Common. 
Of these minerals, mica, hornblende, and sulphur are, so far 
as my observations go, not present in the Krakatao ash. Com- 
paring it with samples from Krakatdo gathered at a comparable 
distance from the scene of eruption, the New Zealand ash suggests 
a more hastily formed material, the minerals in common being 
less perfectly developed in the New Zealand ash. I have not 
noticed as yet in this ash the hypersthene conspicuous in that of 
Krakatdo. There are some organic remains, calcareous frag- 
ments of shells. J. Joy 
the main haulage roads supplied at convenient distances with | _ Physical Laboratory, Trinity College, Dublin, October 18 
