6 
not reached by the spray from getting a foothold. Crude petroleum 
comes in a great many different forms, depending upon the locality, 
the grade successfully experimented with in the work of this Bureau 
showing 43° Baumé. Crude oil showing a lower Baumé than 48° is 
unsafe, and more than 45° is unnecessarily high. The lower specific 
gravity indicated (43°) is substantially that of the refined product, the 
removal of the lighter oils in refining practically offsetting the removal 
of the paraffin and vaseline. The same cautions and warnings apply 
to the crude as to tbe refined oil. 
The oil-water treatment.—Various pump manufacturers have now 
placed on the market spraying machines which mechanically mix kero- 
sene or crude petroleum with water in the act of spraying. The attempt 
is to regulate the proportion of kerosene so that any desired percentage 
of oil can be thrown out with the water and be broken up by the nozzle 
into a sort of emulsion. Some of these machines, when everything is 
in good working order, give fairly satisfactory results, but absolute reli- 
ability is far from assured. The best outlook for good apparatus of this 
sort seems to be in carrying the oil and water in separate lines of hose 
to the nozzle, uniting them in the latter, and in maintaining an abso- 
lute equality of pressure on both the oil and the water tanks by employ- 
ing compressed air as the motive force, kept up by an air pump, the 
air chamber communicating with both of the liquid receptacles. One 
or more manufacturers are now working on apparatus of this general 
description. A 10-per-cent-strength kerosene can be used for a sum- 
mer spray on trees where the San Jose scale is multiplying rapidly and 
where it is not desirable to let it go unchecked until the time for the 
winter treatment. The winter treatment with the water-kerosene 
sprays may be made at a streneth of 20 per cent of the oil. Applica- 
tions of the oil-water spray should be attended with the same precau- 
tions as with the pure oil, and there is even somewhat greater risk, owing 
to the natural tendency one has to apply the dilute mixture much more 
freely than the pure oil. The application should be merely enough to 
wet the bark and should not, to any extent, at least, run down the 
trunk. The collection of water and oil about the trunk is just as dan- 
gerous to the tree as the pure oil. 
In the use of the oil sprays noted above, one wao has not had expe- 
rience with them is advised to make some careful preliminary tests to 
fully master the process, preferably waiting two or three weeks to 
determine the results before entering on the general treatment of the 
orchard. It is well, also, with the oil-water mixtures to test the pump 
from time to time, spraying into a glass jar or bottle to determine by 
actual measurement whether the correct percentages of oil and water 
are being maintained. 
Petroleum-soap emulsions.—The kerosene-soap emulsion, following 
chiefly the Riley-Hubbard formula, has been one of the standard means 
