2 
Transactions Texas Academy of Science. 
[34] 
These samples were to be allowed to stand in snitable glass settling tubes 
for one week — the tubes being filled to a depth of twenty inches. At the 
end of a week the depth of sediment at the bottom was to be noted, and 
from this and the original depth of water the percentage of silt was to 
be determined. A further period of settlement was to be allowed and 
the depths read at the end of one month to determine what further 
subsidence took place. 
Eight settling tubes were sent me and on their arrival I found them 
so irregular in bore that it was necessary to calibrate them the first 
thing. Their capacities varied from 286 to 377 cubic centimeters, when 
filled to a depth of twenty inches, and they were not uniform in size. 
I first made a scale that could be read to thirty seconds of an inch and 
calibrated the lower portion of the tubes so that the volumes correspond- 
ing to given depths were known. With large quantities of sediment in 
the water this method gave fairly good results, but with small quantities 
the percentages were entirely too high. So I procured a number of 
narrow tubes, graduated to fractional parts of a cubic centimeter, and 
after allowing the water to settle perfectly clear in the large tubes I 
decanted it and transferred the sediment to the small graduates, using 
enough water to carry over all the sediment and to fill the tubes to a 
depth of about seven inches. The contents of the small tubes were 
allowed to stand for one week and the volumes of silt read at the end 
of that. time. Occasional samples were allowed to stand for thirty days, 
to note what further subsidence took place. For the few samples that 
I was able to allow to stand for this length of time I found that the 
volume of the silt at the end of one month was about one-tenth less than 
the volume at the end of one week. One set of four samples showed 
even greater reduction in volume. It was set in the small tubes on the 
20th of November. 1900, and at the end of one week showed an average 
of 3.8 per cent, of silt. On the 20th of December it showed only 3.21 
per cent, of silt — a reduction of nearly one-sixth as compared with the 
volume at the end of one week. Lack of a sufficiency of settling tubes 
has prevented me from carrving the settling process still further. Pro- 
fessor Arthur Goss, of the New Mexico Experiment Station, found for 
one set of samples that was collected on December 4, 1899, that, at the 
end of one month, the silt at the bottom of the tubes amounted to about 
4.4 per cent, of the original volume of water. This sample was taken 
from the Bio Grande river at Earlham Bridge, New Mexico. At the 
end of eleven months Professor Goss again read the depths of silt in 
the tubes and found an average of about 3.75 per cent, of sediment — 
a reduction during ten months of about 15 per cent, of the volume at 
the end of one month. From the results of my own and Professor 
Goss’s tests I have concluded that if the percentages a>t the end of one 
week be reduced one-fourth it will give a result that will not be less 
