io The: Colorado Expe:rimknt Station. 
with which we are dealing is to express it in tons per acre-foot as 
was done in Bulletin 155 or in the surface two inches of soil. The 
figures obtained for the August sample gave us 22.1 tons in the 
top two inches of soil for each acre of land or practically 133 tons 
per acre-foot which corresponds to 6.66 percent of the weight of the 
air-dried soil. These trees had lived and grown healthily, some 
of them I would say vigorously, for fourteen or fifteen years, till 
May, 1909, when twelve or more of them- died within a fortnight 
without previously having shown any distress and within the next 
eighteen months eight acres or more of this orchard died. 
Case No. 6— My first observations on this orchard were made 
in 1908. Some trees scattered throughout the orchard had already 
died and been removed. While I was satisfied that arsenic, had 
caused the death of some of them, it evidently had had nothing 
to do with the death of others. At first I had considered seepage 
to be the possible cause of the trouble. The water plane, however, 
was stated to be from seven to ten feet below the surface. Subse¬ 
quent investigation indicated that this statement was correct, be¬ 
sides my knowledge of this section of the country would lead me 
to expect the water plane to be not less than six feet below the 
surface. I do not believe that the water plane rises and falls 
through any great distance, at least I have found no indications 
of such a fact. The owner stated that the ground turned brown 
and then things' died. The aspect of the land is to the south with 
a slight depression running northeast and southwest through the 
orchard. There are some differences of level in different parts of 
the orchard. I have no notes in regard to the amount of these dif¬ 
ferences but they are not great, possibly a maximum of twelve feet. 
A cellar is located near the middle of the east side of the orchard 
and it is five feet deep with a hole dug about the middle of it. 
This hole had some water in it in the spring of 1909. More trees, 
eighteen of them, died during the latter part of the season of 1908 
and these were removed in the spring of 1909 after which the 
orchard was plowed and this portion of it sowed to wheat. The 
wheat was a total failure as almost none of it came up. The 
owner attributed this to his failure to irrigate the land. My 
opinion is that it was not his fault. By July 1, 1909, the orchard 
was very badly burned and by October a portion of it was dead 
and leafless. Photographs of this orchard were used as illustra¬ 
tions in Bulletin 155, Plates III and IV, page 26. As Plate III 
shows the healthy condition of that portion of the orchard which 
formed the background of Plate IV, which gives an excellent 
idea of how the orchard had suffered, they are reproduced in this 
connection as Plate I. This represents the destruction wrought in 
a single season. These trees, no of them, were removed in the 
spring of 1910, and on July 14, the date of my next visit, the 
