20 THE SMOKE INVESTIGATION 



EXPERIMENT V. 



Begun July 2, 1913. Selected Fir plants in the Col- 

 lege nursery. Applied small quantities of soot every other 

 day until about July 21, 1913. Quantities were of Sample 

 C. The following amounts were used: Case No. 1, 3.78 

 gm. per square meter. No. 2, 2.97 gm. per square meter. 

 No. 3, 3.6 gm. per square meter. No. 4, Control. 



At the end of the experiment all plants seemed to be 

 in good condition. No difference could be seen among 

 them. 



EXPERIMENTS WITH PEA SEEDLINGS. 



(a) Samples of soil taken from the surface and at 

 a distance of two inches from the surface from near the 

 mills at Homestead and tested for the presence of toxic 

 gases by a method devised by Crocker, Knight and Rose 

 (8) gave negative results. 



(b) A few experiments with etiolated seedlings gave 

 slightly positive results. They consisted of a modified 

 Crocker type as follows : A can of 50 liters' capacity was 

 placed over the etiolated seedlings and sealed around the 

 bottom with oiled clay. It was further provided with an 

 opening through the upper edge which permitted the ap- 

 plication of soot to the seedlings. At right angles to and 

 below this opening a shaft passed through the can and 

 bore a fan on the inside. On the other end of this shaft 

 was a pulley to which a motor was attached. This motor 

 was also connected with a blower which in turn was con- 

 nected to the can by means of a rubber and tin tu'be ( Fig. 

 16). The tin tube was similar to the one used in the field 

 experiment. The soot was applied by placing small quanti- 

 ties in the tin tube. It was then forced and distributed 

 into the case by running the blower at high speed simul- 

 taneously with the rotation of the fan. 



These experiments were repeated a number of times 

 with similar outcome so that one experiment will suffice 

 to illustrate the character of the results obtained. Etio- 

 lated seedlings of sweet pea grown on moist cotton were 

 used. After they had grown 2 to 3 cm. they were placed 



