THE USEFUL DIATOM 



There is, however, a distinct annual harvest of these 

 minute seaweeds, of which different sorts appear to develop 

 one after the other, just as flowering plants do. The two 

 months January and February, which are almost without 

 flowers, are also those in which most of these minute 

 vegetables take their repose in the form of cysts or spores. 



But these diatoms are too important and too interesting 

 to be dismissed in such a cursory manner. Each consists of 

 a tiny speck of living matter with a drop or two of oil en- 

 closed in a variously sculptured flinty shell. They have, in 

 fact, been compared to little protected cruisers which pass 

 to and fro in the water and multiply with the most extra- 

 ordinary rapidity. 



If you (1) use dynamite to blast a rock, (2) if you 

 employ a microscope or telescope, (3) if you paint an oil 

 picture, (4) if you make a sound-proof partition in a set of 

 offices, the probability is that it has been necessary to use 

 the substance diatomite in each case. This consists of the 

 accumulated shells of myriads of diatoms. 



Nor does that represent by any means the whole of the 

 usefulness of these tiny seaweeds. The oil shales, such as 

 occur in Linlithgowshire and elsewhere, are supposed to be 

 the muddy, oily deposits of such ponds as we have en- 

 deavoured to describe. The oil found in the shales was 

 probably worked up by these diatoms in long-past geological 

 ages. It may be used to-day either (1) to drive motors, 

 (2) to light lamps, (3) to burn as so-called " wax " candles, 

 (4) to eat (as an inferior soii: of chocolate cream). 



Interesting as these diatoms are, it is not really possible to 

 understand their structure without the use of a microscope, 

 so that we must pass on to another side of the activity of 

 water plants. 



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