~146 
NATURE 
[Fune 19, 1873 
7. When the external organs arrive at this final form 
before the organs of reproduction are matured, these 
changes are known as metamorphoses ; when, on the 
contrary, the organs of reproduction are functionally per- 
fect before the’ external organs, or when the creature has 
the power of budding, then the phenomenon is known as 
alternation of generations. 
8. Thus, then, it appears probable that these remark- 
able phenomena may have arisen from the simple cir- 
cumstance that certain animals leave the egg at a very 
early stage of development, and that the external forces 
acting on the young are different from those which affect 
the mature animal. 
JOHN LUBBOCK 
(To be continued.) 
ON AN IMPROVED FORM OF OZONE 
GENERATOR 
SHORT description of an improved form of ozone 
generator, exhibited at the last meeting of the 
Chemical Society, may perhaps be interesting to the 
readers of NATURE. 
Probably no apparatus hitherto introduced, for the pro- 
duction of ozone by clectric induction, has in its working 
given universal satisfaction, The original form of “ Sie- 
mens’ tube ” has many disadvantages, amongst which the 
chief are, the extremely fragile nature of the two glass 
tubes, especially when sealed together by the blowpipe, 
and the fact that if the apparatus be worked for any 
length of time it becomes heated, thereby causing a dimi- 
nution in the quantity of ozone obtained. The arrange- 
ment of a number of glass plates coated on alternate 
sides with tin foil, and enclosed in a box, known as 
“Beane’s” instrument, possesses—especially if used as 
it is intended it should be with a large and powerful 
coil—this latter disadvantage to a considerable extent. 
Sir Benjamin Brodie, during his researches upon ozone, 
used a modification of “ Siemens’ tube,” which in a great 
degree overcame this difficulty. Two glass tubes closed at 
one end, and of such diameter that one was capable of 
sliding within the other, were fixed together in that way, 
the junction being effected either by the blowpipe or by 
means of paraffin, thus leaving a small annular space 
between them through which the oxygen or other gas to be 
ozonised could circulate ; tin foil coatings were dispensed 
with altogether, the inner tube being filled with water, 
and the whole apparatus stood in a vessel of water, wires 
in conection with an induction coil being placed in the 
interior tube, and also in the outer vessel: this water 
could be kept cool by ice, and thus any heat produced 
he 
during the time it was in use was successfully neutral- 
ised. Such an apparatus works exceedingly well but 
requires delicate handling, and is not perhaps very well 
adapted for having other pieces of apparatus attached 
to it. 
This new instrument is an improved modification of 
the above, but permits of a continuous stream of water 
of any required temperature being maintained through it ; 
and further, the annular space which in the case of glass 
tubes is often very irregular, causing thereby an unequal 
electrical discharge, is made as true as possible, and the 
result is a more uniform conversion of the gas into ozone. 
The apparatus as at present made will be better under- 
stood by the following description referring to the accom- 
panying diagram :—A A isa piece of glass tube of a little 
more than one inch in diameter, and of as uniform a bore 
as can be obtained. On each end of this tube is placed 
a brass cap, bored with two holes, and coated inter- 
nally with shellac ; in the interior of this glass tube and 
of a diameter scarcely less than that of the tube itself, 
but not quite so long, is placed a thin hollow brass box, 
B B, with its surface made as true as possible by turning 
in a lathe; this brass box is placed concentrically with 
the outer tube and is completely coated on its ex- 
terior surface with tin, the tin being acted upon to the 
smallest extent by the ozone. This hollow box communi- 
cates with the exterior of the apparatus by means of the 
ccc 
New Ozone Generator. 
tubes C C passing through the centre of the caps. It is 
intended that a current of water shall be kept circulating 
through the interior of this box, the water being brought 
into direct contact with its sides by means of a small 
spiral placed within it, the box being of a slightly less 
diameter than the glass tube, a small annular space wi 
remain between the two, and through this space the gas 
to be ozonised is passed by means of the tubes D D; the 
box itself is made one of the electrified surfaces, and a 
strip of tin foil G, fixed to the outside of the glass tube, 
forms the other ; two binding screws, E and F, serve to 
make the necessary connections with an induction coil. 
The production of ozone by this apparatus is exceed- 
ingly regular and constant. No quantitative estimations 
with iodide of potassium and sulphurous acid have as yet 
been made with regard to the amount of ozone obtained, 
but an approximate experiment upon the quantity of 
indigo bleached in a given time, seems to indicate that 
this amount is quite equal to, if not rather in excess of, 
that obtained when the ordinary apparatus is used. This 
instrument possesses also some minor advantages ; it is 
not so easily broken, other pieces of apparatus are very 
readily attached to it, and at the same time its cost is 
less. There appears to be no reason why larger forms — 
should not be manufactured upon the same principle. 
These instruments are made by Messrs. Tisley and Spiller! 
of Brompton, THOS. WILLS 
