THE ORCHID REVIEW. 83 
With the object of testing this matter the following series of 
experiments were instituted. A definite quantity of a mixture of equal 
parts of ordinary soot and calcium hydrate (slaked lime) was placed in 
three test tubes, each covered with a glass slip, to the under side of which 
adhered a moistened piece of red litmus paper. The paper was changed 
every morning and its condition carefully noted. 
No. I. tube contained the dry mixture. 
No. II. the soot and lime wetted to the consistency of paste. 
No. III. had four times as much water added. 
The paper in No. I. was practically unaffected during the fortnight 
covered by the tests, and probably if moisture had been altogether absent 
it would have been completely so. 
The time required for the litmus paper in Nos. II. and III. to entirely 
change to a blue colour, indicating the presence of the gas, varied from 
about two minutes from the commencement of the experiments, to half an 
hour and an hour respectively at the end, showing that a gradual but 
diminishing quantity was given off each day. 
The temperature of the room was about 63 degrees throughout, but it 
is probable that in greater heat, such as is maintained in a stove house, the 
gas would have been more rapidly but less lastingly evolved. 
A curious point observed afterwards, when water was mixed with No. 1, 
was that the paper im a few seconds showed the presence of the alkali, 
indicating that the properties of the mixture were not merely dormant but 
increasingly active. 
I gather from these experiments that the dry mixture of soot and lime 
preserves its power of giving off ammonia, when wetted, for a considerable 
period, and that this evolution is extended in a decreasing amount over 
several days. I intend during the coming growing season to give the use of 
it a trial in my small general collection, by spreading the dry mixture on 
the cinder-covered stages, and leaving the usual ‘‘ damping down ”’ to supply 
the requisite moisture. 
Liverpool. F. H. Moore. 
‘This experiment is very instructive. We have long thought that 
mixing the ingredients in a tub with water was unnecessary labour, as these 
might be mixed dry, and a handful sprinkled occasionally over the cinders 
when damping down, and the moisture of the house would do the rest. 
The waste of the gas affords an additional argument. Do not overdo it by 
using too much. A little and often is probably a safe rule to follow, and the 
season when it is likely to do most good is when active growth is taking 
place.—Eb.| | 
