116 THE MICROSCOPE. Aug. 



and it can be carried on in the ordinary flat-mouthed 

 bottle without danger of cracking it. 



When it is in action the carbon dioxide is very little 

 and no danger of poison is to be anticipated, for carbon 

 dioxide (carbonic acid) must be in a vast majority in the 

 air to be poisonous, and then its first action is to cause 

 sleep. So, as I have said, there is no danger from poi- 

 son in the process. While it is hot the bottle is placed 

 out of doors, or at a window, so that the fumes which are 

 going to be made by the addition of another liquid to 

 it and which are poisonous may be carried off and not 

 be inhaled, as that causes coughing. Hydrochloric 

 acid (muratic acid of the shops) is added drop by drop. 

 Immediately a brisk effervescence is developed, and 

 bright red fumes are given off. These fumes are those 

 that cause coughing. Enough hydrochloric acid is ad- 

 ded to give off all the fumes, and, though the quantity 

 can not be estimated, it is best to add enough, because 

 the acid is cheap. 



The bottle is permitted to stand about fifteen minutes, 

 until the action has ceased, and then fresh filtered wa- 

 ter is added in quantity. It is washed in filtered water 

 three times, until it becomes light yellow in color. Then 

 household ammonia is added (I use household ammonia, 

 as it is cheap and strong enough), and it is washed with 

 plenty of filtered water. I always use filtered fresh 

 water for washing baciliarian shells, as I thereby obviate 

 the chances of introducing foreign forms, since these 

 can be introduced very readily, and the gathering is 

 thereby ruined and made useless. This is the entire 

 manner of cleaning recent fresh water shells. They 

 can afterwards be kept in fresh water which has a little 

 true salicylic acid added or oil of cinnamon. This will 

 prevent the appearance of bacilli or of larger fungi. 



With salt water recent gatherings of bacillariacese, the 



