A. J. Downing,

Esq.: It has been the study of a great many practical men and amateurs, of late years, to devise some means for the destruction of the curculio; but as yet, I believe, with no considerable degree of success. Although I have read in your Journal the reports of various gen-tlemen, stating their entire success in extirpating this insect, I am led to believe their discoveries have not led to any general results.

I have never as yet seen in the writings of any persons on this subject, any invitation to visit their place, for the public to be convinced of their success. The depredations of this worst of all pest, have attained such a magnitude that I think any party claiming to be able to subdue the curculio, should offer proofs of their theory by saying, come and see, and believe." Occular demonstration is satisfactory to all parties. This I suggest, because then no one will be led astray.

I will now, state to you my experience with the curculio. Being gardener for near 7 years, for Col. T. H. Perkins, Brookline, Mass., one of the best and most extensive private gardens in the country, I was, while there, indefatigable in my exertions to find out some method to exterminate the curculio, but without avail.

In the year 1848,I left that place, and went south and west. During all thaf time, the destruction of the curculio was my principal object. I was last summer gardener upon the place of Mr. Long worth, and I can with truth plums in his whole establishment for the year. Leaving west, I came to New-York, and obtained a situation with W. C. Langley. Esq., a patron and friend of horticulture, and a gentleman who has spared no expense in furnishing his establishment with the choicest fruits - the plum in particular. Here I again commenced my labors, and I am happy to say, with perfect success; and as mere assertion is worth little. -I invite all unbelievers, as well as inquirers, to occular demonstration.

Mr. Langley has an extensive and beautiful plum orchard, and this year in particular, it was loaded with fruit, all the trees bearing about equally. For an experiment, I commenced the application with a quill, of a new composition, on three trees. The result is worthy of being seen. There is not a plum in the orchard, except on these three trees, they having fallen off, destroyed by the insect. To one of the three I shall be obliged to apply props, otherwise it will break down. I can only add, that I am convinced that my composition is a radical exterminator. I shall keep its nature private until practical men, and others interested, are satisfied. Mr. Langley's place will be open for the public to examine for themselves, after which my receipt shall be open to the world. The compound for 100 trees would not cost over eight dollars. It is applied with a syringe. I am sir, your humble servt., "Wm. Quant, Gardener to W. C. Langley, Esq., 3d Avenue. Long Island, July 12, 1851.