60 THE SAN JOSE SCALE. 
and derrick for inediuni-sized trees cost from $15 to $25; for a tree 30 
feet tall by 60 feet in circumference, about $60. 
Fused potassium cyanide (58 per cent pure 1 ), commercial sulphuric 
acid, and water are used in generating the gas, the proportions being 
1 ounce by weight of the cyanide, slightly more than 1 fluid ounce of 
acid, and 3 fluid ounces of water to every 150 cubic feet of space. 
Place the generator (any glazed earthenware vessel of 1 or 2 gallons 
capacity) on the ground within the tent, and add water, acid, and 
cyanide, the latter in lumps, in the order named. Allow one-half hour 
for large trees or fifteen minutes for small ones. Bright, hot sunlight 
is apt to cause injury to foliage or new wood. This may be avoided 
by using tents of dark material, or working on cloudy days, or at 
night. One series of tents will answer for a county or large commu- 
nity of fruitgrowers. 
Method of fumigating nursery stock. — In the case of nursery stock the 
treatment maybe often given most economically and with the least pos- 
sible trouble after the stock is removed and brought together for ship- 
ment. Large batches of stock can be heeled in, compactly tented over, 
and fumigated rapidly and with little difficulty. The dormant condi- 
tion of the plants at this time will practically obviate any danger of 
serious effects of the gas on their vitality. 
Mr. W. E. Gunnis, chairman of the San Diego County board of hor- 
ticultural commissioners, writes us, under date of June 24, 1894, that 
m the case of his first experiment with this gas he treated 40,000 trees, 
nursery stock, averaging 8 feet high. These trees, which were badly 
infested with San Jose scale, were heeled in and fumigated by covering 
with large sheets and using several large generators, distributed accord- 
ing to size of the section of trees covered. No living scales have ever 
been reported on these trees since. 
The possible use of a much greater strength of cyanide on dormant 
nursery stock is indicated by later experiments conducted by Mr. 
Gunnis and communicated to us in a letter dated January 30, 1896. 
He reports fumigating a very large lot of nursery stock after the man- 
ner just described, using, however, one ounce of cyanide of potassium 
98 per cent pure for each 100 cubic feet of space to be filled by the gas. 
When a considerable space was included three or four generators were 
employed. For instance, in one section estimated to contain 4,000 
cubic feet of space four generators were used, each containing 10 ounces 
of cyanide, 12 fluid ounces of sulphuric acid, and 30 ounces of water. 
These were placed in the passages between the trees, the cyanide and 
water being mixed first. The acid was added afterwards, beginning 
with the generator farthest from the opening and passing rapidly to 
the others, care being taken meanwhile not to breathe. The gas was 
allowed to act for one hour. The work was done in December at night 
and the trees were afterwards set out in orchards. They were subse- 
quently inspected several times and no living scales found on them. 
^his strengtk should be guaranteed, or, preferably, shown by chemical analysis. 
