Deviations of the Compass on Iron and Wooden Steam-ships. 581 
given time, especially in the case of Leguminous crops, is not satis- 
factorily explained by reference to the hitherto quantitatively deter- 
mined supplies of combined nitrogen. 
The results and conclusions hitherto recorded by different experi- 
menters on the question whether plants assimilate free or uncom- 
bined nitrogen, are very conflicting. 
The conditions provided in the experiments of the Authors on this 
question were found to be quite consistent with the healthy develop- 
ment of various Graminaceous Plants, but not so much so for that of 
the Leguminous Plants experimented upon. 
It is not probable that, under the circumstances of the experiments 
on assimilation, there would be any supply to the plants of an unac- 
counted quantity of combined nitrogen, due to the influence either 
of ozone, or of nascent hydrogen. 
It is not probable that there would be a loss of any of the com- 
bined nitrogen involved in an experiment on assimilation, due to the 
evolution of free nitrogen in the decomposition of organic matter, 
excepting in certain cases when it might be presupposed. 
It is not probable that there would be any loss due to the evolu- 
tion of free nitrogen from the nitrogenous constituents of the plants 
during growth. 
In numerous experiments with Graminaceous plants, under a wide 
range of conditions of growth, in no case was there any evidence of 
an assimilation of free nitrogen. 
In experiments with Leguminous plants the growth was less satis- 
factory, and the range of conditions was, therefore, more limited. 
But the results with these plants, so far as they go, do not indicate 
any assimilation of free nitrogen. It is desirable that the evidence 
of further experiments with such plants, under conditions of more 
healthy growth, should be obtained. 
Results obtained with some other plants, are in the same sense as 
those with Graminaceous and Leguminous ones, in regard to the 
question of the assimilation of free nitrogen. 
Tn view of the evidence afforded of the non-assimilation of free 
nitrogen by plants, it is very desirablé that the several actual or 
possible sources whence they may derive combined nitrogen should 
be more fully investigated, both qualitatively and quantitatively. 
If it be established that plants do not assimilate free or uncom- 
bined nitrogen, the source of the large amount of combined nitrogen 
known to exist on the surface of the globe, and in the atmosphere, 
still awaits a satisfactory explanation. 
** Reduction and Discussion of the Deviations of the Compass ob- 
served on board of all the Iron-built Ships and a selection of the 
Wood-built Steam-ships in Her Majesty’s Navy, and the Iron Steam- 
ship ‘ Great Kastern’.”’ By Frederick J. Evans, Esq. 
The analysis of the deviations of the compass in this paper com- 
prises the observations made in forty-two iron ships, varying in size 
from 3400 to 165 tons, a selection of wood-built screw and paddle- 
wheel steam-vessels, as also the steam-ship ‘Great Eastern’ at various 
_times prior to her departure from England. 
M2 
