262 
might also have a naval reserve, to be employed chiefly 
on board the mercantile cruisers and liable to service for 
a short period every year or two on board a commissioned 
ship of similar type. 
Referring to harbour defence, Sir William pointed out 
that many of our ironclad forts had already become obso- 
lete, and gave the place of first importance to gunboats, 
in combination with torpedo launches and submarine 
mines, all of which he suggested might be managed by a 
well-trained corps of volunteer engineers resident on the 
spot. Here again it is evident that Sir William does not 
think, great though our present expenditure is, that 
enough is done for the efficient protection of the country, 
and rather than advise an increased outlay he judiciously 
seeks, by the improvement of the system, to obtain better 
results for the same money. 
Sir William then referred briefly to the progress made 
in the manufacture of guns since the introduction of 
rifling, but made no special allusion to the improved 
breech-loaders constructed by his own firm for foreign 
powers, and which have long been known to be much supe- 
rior to anything in our own service; in fact, while guns 
of this type are now beginning to receive the serious con- 
sideration of our Government departments, their original 
designers have for some time turned their attention to 
something newer still and far more powerful. Sir William 
shortly described the latest system upon which experi- 
ments are being made at Elswick. In this system the 
coils surrounding the central tube consist of steel ribbon 
wound on spirally at a certain tension. It is apparent 
that no longitudinal strength is obtained in the coils by 
this method ; and to supply this deficiency, longitudinal 
layers of ribbon steel are interposed at every fourth cir- 
cular layer. = 
The advantages of the system are that steel, in the 
form of wire or drawn ribbon, possesses far greater tena- 
city than in any other form, and that the initial tension 
at each point in the coils of the gun can be accurately 
adjusted. The first gun of this type was a 6-inch breech- 
loader, tried in the beginning of 1880, and so satisfactory 
were the results, that a 1o-inch gun of 21 tons weight has 
since been constructed, and is now under trial, 
The importance of working heavy guns on board ship 
by engine-power was pointed out as lessening the number 
of men exposed, and the objection that the machinery 
was liable to be disabled by an enemy’s fire, was shown 
to apply equally to the mechanism required for hand- 
power. 
In concluding Sir William adverted to a subject of 
grave importance. “Our navy was at present armed 
with guns whieh could not be expected to contend suc- 
cessfully with the best modern guns that could be brought 
against them.” ‘Our service guns had simply been 
overtaken in that rapid progress of artillery which had 
been going on for the last eight or ten years,” 
“Tn the mean time no expense should be spared in 
judicious experiments, seeing that the expense of experi- 
ments was trifling in comparison with that of mistakes. 
Above all, the Government should pursue such a course 
as would bring into full play the abundant engineering 
resources of this highly mechanical country, for increasing 
the efficacy of our national defences.” 
On this last and most important point we have before 
laid stress in these columns. We have before pointed 
NATURE 
[Fan. 19, 1882 
out that the keen commercial competition for foreign 
orders amongst private firms fosters a vitality and 
vigorous growth in the direction of any improvement or 
new development which is invisible, and would probably 
be felt inconvenient in our Government factory. It would 
surely then be to the advantage of this country to avail 
ourselves of the energy and enterprise of our private firms 
instead of allowing them chiefly to benefit our foreign 
competitors. 
THE SUN 
The Sun. By C. A. Young, Ph.D., LL.D. International 
Scientific Series. (Appleton, New York.) 
INCE the method of artificial eclipses was introduced 
in 1868 Prof. Young, the author of the book under 
notice, has from time to time done good work in utilising 
the capital climate of his native country and his relatively 
superior optical means to confirm in many essentia] 
points and to add a little shading here and there, to the 
bold outlines of the new science, for which we are in- 
debted to his predecessors. 
The book, which deals with the sun in the most general 
manner, will be read with interest, as its style, though not 
brilliant, is popular, and such questions as the sun’s dis- 
tance and the various instrumental means now at the 
disposal of astronomers for increasing our present know- 
ledge are very clearly referred to, while those whose 
acquaintance with spectrum analysis is not very intimate, 
will be able to gather from the volume much interesting 
information conveyed in an agreeable form. 
To those who have followed with some keenness the 
recent progress of solar physics that part of Prof. Young’s 
book which refers to the hypothesis of the dissociation of 
the elementary bodies at the temperature of the sun will 
possess much interest, the more so as the author has been 
freely quoted as objecting to the hypothesis zz fo/o. 
On this account we do not think it inappropriate to 
give in Prof. Young's own words his views on this point 
It is the more important to do this because very few 
beyond the number of those who have been more or less 
engaged in the inquiry have any conception of the re- 
markable character of the facts which have been accumu- 
lated during the last thirteen years, or of the way in which 
they refuse to be included in the previous hypothesis 
according to which we were really in presence of ter- 
restrial elements in the sun and stars, the old hypothesis 
being based upon the asserted identity of the solar and 
stellar spectra with those seen in various terrestrial light 
sources. 
The extracts run as follows :— 
“When we recollect that the non-apparent elements con- 
stitute a great portion of the earth’s crust, the question at 
once forces itself : What is the meaning of their seeming 
absence? Do they really not exist on the sun, or do they 
simply fail to show themselves; and, if so, why? The 
answer to the question is not easy, and astronomers are 
not agreed upon it. Mr. Lockyer has, however, proposed 
a theory which, if established, would remove most if not 
all of the spectroscopic difficulties. He thinks that our 
elements are not really elementary, but built of molecules 
themselves composite and capable of dissociation by the 
action of heat. Thus, a mass of chlorine, for instance 
may at a certain temperature break up into constituents 
