60 PAUL J. ANDERSON 



1495 from a recently macadamized road where the percentage of 

 Hmestone was high. 



Table II gives an analj^sis of cement dust collected from the 

 same locality and analyzed by Prof. Enrique Touceda of the 

 Troy Polytechnic Institute. 



Three points should be noticed in these analyses: (1) The 

 soil and road dust sample show such striking differences from 

 cement dust in the proportion of constituents that neither of 

 them could possibly be the source of the dust on the leaves; (2) 

 a large part of the limestone in the cement dust has had the 

 carbon dioxide removed and the lime is left in the caustic condi- 

 tion. Sample 1452, for instance, contains 12.10% of carbon di- 

 oxide. If the lime and magnesia here were in the form of a nat- 

 ural limestone — i.e., calcium and magnesium carbonates, as they 

 are in the road dust sample 1495 — the dust should contain 37.78% 

 of carbon dioxide. In other words, over two-thirds of the lime- 

 stone has had the carbon dioxide removed from it — a condi- 

 tioit which could be brought about only in the kilns. (3) Nearly 

 8% of the dust is lime that is soluble in water. The soluble 

 lime is the cause of the extreme alkalinity of the dust and, as 

 will be indicated below, is probably the source of injury to the 

 fruit blossoms. 



Less fruit on the dusted side of the trees. Our first observations 

 were in the summer of 1910. During the entire blooming season 

 of that year, a continuous south wind blew the dust from the 

 mills onto a cherry orchard where our laboratory was estab- 

 lished. The blossoms on the south side of the tree were literally 

 plastered with dust while those on the north side were more or 

 less protected. When the fruit was about half grown, the num- 

 ber of cherries on each side of eighteen trees were counted and 

 there was found to be 29% more fruit on the north side than on 

 the south side of the trees. The same number of trees outside 

 the dust zone were counted as a check and it was found that there 

 was a difference of only 2.2% in the number of cherries on the 

 south and north sides and that in favor of the south side. This 

 led us to suspect that the dust did in some way influence setting 

 of the fruit. 



