32 



than the proper quantity were nsed the whole of the gas would not be evolved from the 

 cyanide solution ; hence the advisability of always using an excess of the acid. 



In generating the gas the acid should flow upon the cyanide solution in a very fine 

 stream. When they come in contact violent action at once takes place, and the gas is 

 rapidly given off in the form of dense whitish fog, resembling smoke and possessing a 

 peculiar odor. When this gas, diluted with air, is inhaled, it produces a dryness in the 

 mouth and throat. 



It is impossible to give any definite rule for using the different ingredients that will 

 apply to the differently sized trees, owing to the fact that trees of the same height may 

 have a varying diameter of top; thus orange trees twelve feet tall may have a diameter 

 of top ranging all the way from six to ten feet. The manner in which the tree is pruned 

 will also make a difference in the quantity of the ingredients to be used, some trees 

 being allowed to branch almost from the ground, while others are trimmed up from 

 three to five feet from the ground. 



The following table based upon numerous experiments which I have made on orange 

 trees under a tent ten feet tall and having a transverse diameter of ten feet, will give a 

 good idea of the proper quantities of each ingredient to be used in treating citrus trees : 



This table is based upon the cubical contents of the space inclosed by the tent, sup- 

 posing that the lower part of the tent rests upon the ground. No harm will result to the 

 tree if twice the quantit^y that I have recommended be used ; but of course, for the sake of 

 economy, it will be desirable to use only such quantity of each ingredient as will be nec- 

 essary for destroying the scale insects infesting the tree to be treated with this gas. The 

 sulphuric acid should have a density of 65 degrees when tested with an acid hydrometer; 

 should its density be lower than this, use an extra ounce of the acid for every 5 degrees 

 of density below 65 degrees. 



According to Mr. Morse's experiments, however, it has been proved that 

 the injury to foliage was caused by ammonia, which, especially through 

 the direct influence of sunshine, is evolved from the gas confined in the 

 tent, and Mr. Morse suggests, therefore, instead of passing the gas through 

 liquid sulphuric acid, to construct a drier large enough to have it filled with 

 a quantity of pumice stone saturated with sulphuric acid. To test this idea 

 on a larger scale, and to also test the practical workings of the Culver tent, 

 I obtained the consent of the Commission to have an apparatus made. 

 From Mr. J. P. Culver, of Los Angeles, I obtained permission to make use 

 of his drawings and plans, and had a tent constructed according to his 

 idea, with slight moditications except to size of timbers, frame, etc., which 

 were reduced one half, fully, making the whole apparatus so that it could 

 be drawn along on level ground by one horse. The frame and sled on 

 which the tent rests are five and a half by twelve feet, and are made of 

 Oregon pine with runners of oak. 



The tent proper consists of two even halves swung on heavy hinges fast- 

 ened to the mast, and the frame on which the cloth is fastened is made of 

 two by two-inch ash. The curved part of the frame or arch is made of 

 one by two-inch, lapping and bolted together. Where the two frames meet 

 to close the tent a strip of heavy felting is nailed on it. The tent cloth is 

 made of heavy, fine-woven drill, oiled with linseed oil, and is tacked on 

 the edge of the frame. The mast on which the heavy iron hinges are f;ist- 

 ened is made of a four by four, but it would be advisable to have this a 

 little heavier or have it banded with iron. On the top two iron rods, with 

 thumb-screws and thread in the middle, are held in iron hooks. These 

 rods are an essential support for the tAvo wings of the tent when they are 

 swung on the hinges. When a tree is to be treated the frame is drawn 



