AMERICAN INSTITUTE. 403 



Dr. Trimble. — One of the hospital buildings at Philadelphia is covered 

 with slate, and it is found a very cheap roof. It comes from a Pennsylva- 

 nia quarry that produces it at low rates, and it is put on in some new 

 method. 



Wm. S. Carpenter. — The best slate costs $10 the square of ten feet. 

 Tin costs $11, put on the roof. 



Peter G. Bergen. — The iron roof I speak of cost $9 a square. 



Dr. Trimble. — The slate roof I spoke of is put on in some kind of 

 cement, and is laid quite flat. There is a difficulty in all metal roofing 

 about the contraction and expansion that has hitherto prevented its univer- 

 sal adoption. One of the objections heretofore made to slate roofs, is the 

 necessity of making them quite steep. That difficulty is overcome in the 

 roof that I saw in Philadelphia. 



HOW MUCH SUPER-PHOSPHATE PER ACRE ? 



This question come from W. C. George, Charlestown, Mass., who says 

 the farmers there have no experience to guide them, and they always look 

 to the proceedings of this club for information, and therefore wants to 

 know how much super-phosphate should be applied per acre. 



Mr. Robinson. — I answer 600 pounds to begin with, and if that proves 

 a paying application, increase the dose. The object of manuring is not 

 how much can I get along with, but how much I can use profitably. 



Andrew S. Puller. — I knew one person whose hired man applied super- 

 phosphate by the shovelful, and it showed nothing better than upon the 

 adjoining land. Bone dust produced a very decided beneficial effect. 



"Wm. S. Carpenter. — I have never used anything better than Peruvian 

 guano. I use 300 to 500 pounds per acre. It produces beneficial results 

 upon corn and turnips. So does bone dust ; but super-phosphate I have 

 not found profitable. There is so great a difficulty in procuring super- 

 phosphate of a reliable, good quality, that I have given up the attempt. 

 I find the guano the cheapest. 



GUANO AND SQUASH BUGS. 



R. Norton, of Worcester, Mass., after speaking of the interest with 

 which he reads the sketches of the proceedings of this Club, contributes 

 his mite of information to get rid of the yellow bug that infests young 

 squash plants. He says : 



" I have a row of twelve hills of winter squashes — examined them on 

 the second or third day after the plants came up, and found, I should 

 judge, not less than three bugs to a plant, I put a heaping tablespoouful 

 of guano into about four quarts of water, and with the twigs of a bush 

 sprinliled it so as to wet the plants and the ground under them thoroughly. 

 Two days afterward I visited them and found a great swarm, of bugs hover- 

 ing over the plants, but not one on them. I continued the process every 

 third or fourth day until the vines began to run. The yellow bug did them 

 no injury, and the black bugs were unusually few." 



