612 Original Articles. [Oct., 
with, I would recommend them to verify or controvert my statements 
by the following simple experiment :— 
Let them procure some distilled water from a source which is 
certain to be pure; and to make assurance doubly sure, let it be 
boiled, or (as Dr. Rolleston, of Oxford, has suggested*) passed 
slowly through a red-hot platinum tube. 
This water should be exposed in an open situation, in a good-sized 
saucer or soup-plate, and fresh distilled water added day by day, to 
supply the place of that which evaporates. 
The exposure should take place in warm weather, if possible with 
a light breeze, and not too soon after the air has been purified of its 
floating contents by a shower of rain. 
In a few days, if ordinary success attend the experiment, an 
inconsiderable sediment of dust will have settled at the bottom of 
the saucer, and drops of the water, along with a little of this 
sediment, should be submitted to careful microscopic investigation. 
If I am not greatly mistaken, judging from my own experiments, the 
most conspicuous types will be found to be those little fragments 
(more or less definitely shaped) of organized protoplasm known as 
amcebe, and the observer will probably notice many interesting 
phenomena in connection with their growth, permanent changes in 
form, mode of subdivision, &c., to which my limited space has 
allowed no reference. When the field is carefully viewed with a high 
power, there will also probably be found in considerable numbers the 
little fusiform monads (so frequently referred to in this paper), for in 
most of my investigations these have first appeared. 
With favourable weather and perseverance, other and probably 
higher forms will in time become apparent; and I trust that if no 
other good result from the publication of these imperfect observations, 
they may lead more careful investigators to favour the microscopical 
world with valuable contributions to ‘‘ atmospheric micrography ”— 
contributions of a different kind to the negative ones formerly 
published under that title by Dr. Pouchet, the zealous champion of 
heterogenesis. 
For the benefit of those, however, whose time or occupations prevent 
them from investigating for themselves, and who are willing to 
accredit me with accuracy of observation, I have appended a plate, 
which will give some idea of the appearance of the microscopical 
contents of distilled water, after a few days’ exposure to the atmosphere 
in fine weather; but I must state, to avoid misapprehension, that 
although all the forms and others besides may be contained in the 
same drop of water, they will probably not appear at one and the 
same time in the field of the microscope. 
The objects represented in Fig. 1 (commencing at the top) are, 
a fragment of organic matter upon which a swarm of minute 
zoospores and one or two young ciliated infusoria appear to be 
regaling themselves ; then, between the bright crimson hair (animal 
or vegetable) and a green plant fibre, probably one of the confervoid 
* Sub-Section D, British Association, 1863. 
