LONDON-PURPLE. 
105 
in the same manner as Paris-green, but it is stated that owing 
to its lightness a far smaller quantity by weight of London-purple 
will treat a given number of trees than would be required of Paris- 
green. 
One great difficulty in its use in America has been that where it 
is purchased without due caution, merely as a “ waste product” that 
could be had for six cents a pound, or for cost of carriage, there was 
liability to such differences in strength as to lead to much mischief 
where applied without previous testing as to effects. 
It is therefore very desirable to purchase direct from the manu¬ 
facturer (who will furnish analysis) in the case of large quantities, or 
where only small quantities are needed, such as must necessarily be 
procured from retail dealers, either to procure a statement of strength 
(i. e. analysis), which could be had by the retail dealer from the 
manufacturer, or to make careful trial of proportion safe to use, before 
a general application. 
In the note regarding this point with which I am favoured by 
Messrs. Hemingway & Co., of 60 Mark Lane, London, E.C., who have 
long been manufacturers and exporters of this chemical, they mention 
that “ four ounces of London-purple (owing to its lightness) will treat 
the same number of trees as sixteen ounces of Paris-green.” 
This is a matter to be well borne in mind, and in our present state 
of knowledge of effects of this chemical in England, careful experiment 
should always be made by new experimenters as to effects, before 
spraying on a large scale. Also, in a quotation from Dr. Packard 
in the recent issue of “Insecticides,” at p. 33, referring to London- 
purple and Paris-green, it is noted :—“As the effect is slow in appear¬ 
ing, impatient parties will be apt to re-poison on the second or third 
day, and thus put on enough to hurt the plant when the effect does 
come. Much depends on dryness or wetness of the weather ; but good 
effects may be expected by the third or fourth day.” * 
Amongst the points in which the London-purple is considered to 
have advantage over Paris-green is, for one thing, its lower price. 
Looking at returns in my hands from leading manufacturers, wholesale 
prices are stated for the green, as at per cwt., at lOd. per lb., for the 
purple per cwt., at 7d. per lb. This of course I give only as a general 
guide; purchasers would receive definite information from the 
manufacturers. 
Other desirable points are its greater diffusibility in water, also its 
greater adhesiveness to the foliage, and also that this “purple” or 
arsenite of lime is stated not to be so poisonous as the “green” or 
arsenite of copper, although, like the green, the purple is a poison, and is 
* * Insecticides and means of applying them,’ &c., by C. V. Riley, M.A., Ph.D. 
rom Fifth Report of U.8. Entomological Commission. 
