Mr. E. J. Lowe on a new Ozone-box and Test-slips. 467 
Fig. 1. Fig. 2. 
The box has been tested and found to work well. 
On three different dates, when there was much ozone, test-slips were 
hung in one box, whilst others were hung in another which had the 
two entrances sealed up in order that no current of air should pass 
through ; the result was satisfactory, viz. :— 
Example. New ozone-box. New ozone-box sealed up. 
] 10 
2 9 0 
eee gi 0 
Then again, in five examples of test-slips being exposed without 
any box, in comparison with those placed in this new box, the result 
was :— 
Example. In new ozone-box. Exposed to north without 
a box. 
1 10 Ss 
2 9 9 
3 7 7 
4 10 9) 
4) 2 0 
The ozone-box is capable of being suspended at an elevation above 
the ground ; and this appears to be a great advantage, because eleva- 
tion seems necessary in order to get a proper current of air to pass 
across the test-slips ; indeed as an instance it may be mentioned, that 
at an elevation of 20 feet there is almost always more indication of 
ozone than at 5 feet. 
The plan adopted here is to suspend the box to a T support, it 
being drawn up to its proper place by means of a thin rope passing 
over a pulley ; and there is less trouble in examining and changing 
the test-slips in this manner than there was in the old method. 
The box, as described, is made by Messrs. Negretti and Zambra 
of Hatton Garden. 
It has been urged that a box was scarcely necessary for ozone 
test-slips; but as the papers fade on exposure to light, it must be 
evident that in order to register the maximum amount of ozone a 
dark box is required. 
Test-slips.— Paper-slips being so fragile, I have substituted others 
made of calico. The calico is to all intents and purposes chemically 
pure, containing only a few granules of starch, used in the first pro- 
cess of its manufacture, which it is very difficult to remove, being 
enveloped in the cotton fibre ; it is, however, thought to be purer than 
2H2 
