284 The Plant World. 



check it; it continues until others find it a nuisance and protest 

 against it. Instances of this sort are becoming increasingly 

 numerous, because people and industries are coming closer to- 

 gether, affecting each other more directly than when there was 

 so much more unoccupied territory in our country. 



An instance of this sort has come to my notice within the 

 last year. In the San Bernardino Valley in Southern California, 

 the principal occupation of the people is the growing of citrus 

 fruits. The bulk of the yield is oranges, lemons and grape- 

 fruit being produced in less quantity. Orange culture in this 

 valley was established before any manufacturing interest was 

 begun, and many groves of orange and lemon trees had already 

 reached productive and profitable development before any in- 

 dustries not connected with orange culture had come into the 

 vallev. Of late years, however, with the very rapid increase in 

 the use of cement, cement manufacturing plants have been es- 

 tablished and operated in this valley, as well as elsewhere; and 

 those that have been established longest have been greatly in- 

 creased in size and output. 



The manufacture of cement, as ordinarily practiced, is a 

 very dusty business, and unless special pains are taken, the dust 

 will not be confined to the limits, or even to the immediate 

 vicinity of the works. Owing to the nature of the business, 

 the dust which escapes will contain a fair proportion of a product 

 so nearlv finished that a film of this dust will set when moistened. 

 No ordinary dust from road or field would do so. The dust will 

 settle close to the works, or far away from them, according to 

 the fineness of the particles, and according to the wind. There 

 may even be a difference in the proportion of finished product 

 which settles near the works, and that which is carried farther 

 away, because of the difference in the size of the particles. Every- 

 thing in any way exposed in the neighborhood of such works 

 presently becomes covered with a thicker or thinner layer of this 

 dust, to the inconvenience of the housewife as well as of the 

 worker in field and orchard. 



As one goes by Southern Pacific train from Los Angeles to 

 Colton, one passes orange grove after orange grove, the dark, 

 glossy foliage of which gives the landscape a beauty and a char- 

 acter quite unusual. Suddenly one notices, on looking out of 

 the car window, that the leaves of the orange trees are no longer 



