3°7 
of Lime used in Agriculture. 
by being exposed for about the same time as the pure lime just 
mentioned, was only 42 hundredths of that combined with it 
before it was burnt. 
As it seemed probable, that the magnesia contained in this 
lime was the cause of its peculiar properties, the following ex- 
periments were made, to determine the effects of that substance 
upon the growth of vegetables. Some seeds, chiefly of cole- 
wort, which were preferred from their growing quickly, were 
sown in uncalcined magnesia ; but, though they sprouted, the 
leaves never rose above the surface, and the plants were en- 
tirely without roots : nor did they appear to grow better in 
magnesia which had been washed in water containing fixed air. 
Calcined magnesia was, however, much more destructive, as 
the seeds would not come up in it. To compare its effects on 
vegetables with those of lime, each of these earths was mixed, 
in different proportions, with sand, in small cups, in which, seeds 
were then sown. The lime was obtained from marble; and, 
before it was put into the sand, was made to fall to powder, by 
being moistened with water. In a mixture of four ounces of 
sand with three or four grains of calcined magnesia, it was a 
long time before the seeds came up, and the plants had hardly 
any roots or stalks ; and, with ten grains or more of magnesia, 
there was no appearance of vegetation. Thirty or forty grains 
of lime did not retard the growth of the seeds more than three 
or four of magnesia, and the injurious effects were not so last- 
ing. The lime, by absorbing fixed air, soon lost its destructive 
properties; so that, after keeping these mixtures four or five 
weeks, seeds were found to grow in that with forty grains of 
lime, nearly as well as in pure sand; but, in that with four 
grains of magnesia, they produced only the seed-leaves, as was 
