40 
Colorado Experiment Station 
This analysis indicates the presence of about 61.5 per cent, of 
carbonates, almost wholly lime carbonate and a quantity of decompos¬ 
able silicates. The most interesting point, however, is that this marl 
contained 5.21 parts of arsenic, calculated as arsenic acid, per million. 
These marls open the question of the presence of arsenic in our 
marly virgin soils. I have stated repeatedly that the greater part of 
the soils to be considered in this connection are to be considered as 
marly. I have therefore tested some of our virgin soils from land 
not yet brought under irrigation. The two already given cannot 
be considered as virgin soils, i. e., the subsoil twenty-three inches 
below the surface with 15.33 and a marl with 5.212 parts of arsenic 
acid per million. I have determined the arsenic in five virgin soils 
concerning which there can be no mistake about their having never 
received an application of arsenic, at least not the whole five, which 
were taken from localities about sixty miles apart. I found in these 
soils the following quantities of arsenic per million parts of the soil: 
2.8, 3.8, 4.2, 4.5, and 4.7 parts. I have further examined six other 
samples of soils concerning which some doubt might be entertained 
but I am fully satisfied that two of them have never been sprayed 
or received the application of any arsenic whatsoever and still it was 
present. 
In connection with this bleeding I have been confronted with the 
assertion that some of it has been observed in the case of some trees 
which had never been sprayed. I have, not seen such myself but if 
the observation be correct, it would point rather directly to the arsenical 
lime, whether native or artificially added, as the cause of this particular 
trouble, and I believe this to be the case. Those orchards in which 
I have found this trouble the worst are on such marly soil as I have 
described, and so far as I know their history, were treated very liberal¬ 
ly with arsenite of lime, when this preparation of arsenic was exclus¬ 
ively used as a spray material. The samples of virgin soil in which 
the arsenic is present and cannot be attributed to any known source 
contain a comparatively small amount of arsenic compared with the 
orchard soils, in round numbers one tenth as much. This statement 
does not consider the marly subsoil containing 15 parts arsenic acid 
per million because some of this arsenic may have been derived from the 
arsenical spray put on the orchard. No one has, so far as I know, 
attempted to determine to what depth these sprays may affect the 
arsenical content of the soil, but as they are decidedly soluble in water 
it is easy to conceive that the depth to which the arsenic may pen¬ 
etrate is greater than we might think. The sample of soil taken to 
the depth of one foot and showing 138 parts arsenic acid per million 
is also excluded from the above statement that the, orchard soils con¬ 
tain ten times as much arsenic as the virgin marly soils. As our 
transplanted apple trees are shallow rooted, seldom feeding to a 
greater depth than two and one-half feet, it seems probable that the} 
gather their food from the soil proper. I do not think that the, marls 
underlying these lands enter into the question to a great extent, besides 
