426 Report oF THE DEPARTMENT OF ENTOMOLOGY OF THE 
usual amount of an arsenical poison with a diluted sulphur 
solution for the purpose of controlling also the bud moth and 
case-bearer, which are now very destructive in many orchards. 
The arsenite of lime* should be prepared as follows: 
White» arseniois.® ks, in aiis teehee. es ee Sees Tate 2 Ibs. 
Dal soda vcryatals orciecs nonswip% wisut heitin ocean pas ate per ee iaieae 2 lbs. 
VO DEE Sl eed. RM PiU k £ eA iin Sia Batam Bagh Pe kates ana 1 to 14 gal. 
Boil until entirely dissolved, which requires about fifteen 
minutes. Use this solution to slake three or four pounds of 
good stone lime. If this slaking is properly done, the arsenic 
will be combined very effectively, and the arsenite of lime thus 
formed will retain its strength indefinitely. When ready for 
use, add wate, to the product to bring the total up to two gal- 
lons, and stir thoroughly. Two pints of the well-stirred, uni- 
form mixture will then evidently contain one-eighth of the 
original materials or one-fourth pound of white arsenic, in the 
form of arsenite of lime, which is equal to one-half pound of 
paris green. This amount is ample for 50 gallons of diluted 
Spray and it may be added immediately after dilution. 
THE HYDROMETER AND ITS USES. 
To obtain mixtures of definite strength, the lime-sulphur 
solutions should be diluted according to their degree of con- 
centration. The hydrometer is used for this purpose. It is a 
glass instrument, consisting of a weighted bulb with a long 
stem, which determines the weight or density of liquids. Its 
general appearance is indicated in Fig. 11. On the stem of the 
instrument there is a graduated scale, which should be read at 
the general surface of the liquid in which it is supported. 
Hydrometers are of two kinds,— the Beaumé and the Specific 
Gravity, which differ in the standards of measurements on 
which the graduated scales are based. There are instruments 
which have both measurements. Readings on the former are 
given in numerals expressed as degrees, while those on the 
latter are made in decimals. Instruments with a range of 0 to 

* J. P. Stewart. Penn. Sta. Bul.,.92; 
