316 BULLETIN OF THE BUSSEY INSTITUTION. 
closed bottle there was found as much nitrite and nitrate as 
amounted to 0.0003 grm. NH, to the litre. 
I had prepared to study this question of the loss of ammonia 
from water in some detail, when the publication of Houzeau’s 
_experiments upon the subject (Comptes Rendus, 1876, 83. 525) 
induced me to withdraw and leave the field to him. It is notice- 
able that Houzeau’s results differ from mine in that he observed a 
diminution in the amount of ammonia in well-water kept, in the 
light, in closed bottles; while no loss occurred in my samples of 
bottled rain-water. Manifestly different causes were at work in 
H.’s experiments and in mine. 
Besides ammonia, my cistern-water naturally contained traces of 
nitrites and nitrates; but, as the growth of the crops showed, the 
amount of these ingredients added to that of the ammonia was 
not large enough taken altogether to interfere with the experi- 
ments or impair the accuracy of their results. All my experience 
goes to show that rain-water is well suited for the purposes of the 
proposed assay and for other kinds of experiments upon the. 
crowth of plants. 
With respect to the presence of organisms in the cistern-water, 
I find fewer of them there than in most of the sands and loams 
employed in my experiments. After the crops were harvested, I 
examined with the microscope the soils taken from many of the 
jars with the result that while in the sea sands and natural loams 
there was an abundance of small green alge (visible even to the 
naked eye), some diatoms and a few creatures of a higher order, 
the calcined loams and anthracite cinders were comparatively free 
from such inhabitants. There were some green alge, it is true, in 
most of the jars, but I found nothing else in the calcined loams, and 
it seemed plain that most of the organisms found in the sands were 
there originally when the sand was placed in the jars. Even the 
jars which contained the New Jersey green sand (which is a mined 
or quarried product) were free from visible organisms. 
At the time of these examinations I filtered a quantity of rain- 
water from the cistern and examined the residue with the micro- 
scope, but I found nothing but a few round alge and a few opaque 
or black round bodies of unknown character. 
January, 1880. 
