XX THE BEGINNINGS OF II FE. 



wards have become mechanically enclosed within the crystals. 

 A similar chance of contamination by spores derived (either 

 mediately or immediately) from the air would exist during the 

 process of crystallization of the ammonic tartrate itself. 



If the air, however, had been the immediate source of the 

 fungus-spores and masses of confervoid-looking filaments, 

 then such bodies might be found in freshly -prepared 

 crystals just as well as in those which had existed for six 

 months. I therefore asked Messrs. Hopkin and Williams to 

 prepare for me a fresh batch of crystals of neutral ammonic 

 tartrate. This they were kind enough to do; obtaining 

 them in the same place, by the same process, and exposing 

 the mother-liquor in a precisely similar manner. 



An examination of some of these crystals, whilst they were 

 being dissolved in a watch-glass by distilled water, showed 

 that (unlike the older crystals) they were not at all coated on 

 the surface by the comparatively insoluble granular plates, 

 and that only a few very small air bubbles emxCrged from 

 their interior. No trace of the confervoid-looking filaments 

 or of the fungus-spores was to be seen at the bottom of 

 the watch-glass, either during solution or afterwards, though 

 minute shreds of cotton and paper fibres were met with, similar 

 to those which had been found in the older crystals. The 

 examination of a large number of the new crystals was 

 attended with results similar to those just mentioned. 



This absence of the confervoid-looking filaments and of the 

 large fungus-spores from the recently prepared crystals must 

 be accounted for either by one or other of two suppo- 

 sitions : — 



(i). It may be supposed that in the case of the older 

 crystals, the spores and filaments had dropped, as such, into 

 the solutions in which the tartaric acid alone, or the tartrate 

 of ammonia, was crystallizing ; that they were mechanically 

 engaged in the crystals and were subsequently liberated un- 



