I was much oblig’d by your Account of the Effect of the Lightning on Mr. Holder’s House. It will be in the Transactions here. I wonder it is not to be found in yours.
Those here who aimed at obtaining a very great Electric Force, have been much discouraged by the Breaking of the Bottles that compos’d their Batteries. A Gentleman of my Acquaintance lost 8 out of 20 at one Stroke; another 12 out of 40. Having heard that Pere Beccaria had lined the Inside of a great Iron Kettle with Cement, and then coated a Part of the Cement with Tinfoil, from whence he could discharge a great Stroke; and if any Crack happen’d to his Cement, he mended it again with a hot Iron; I recommended trying to make Batteries of Paper, by straining the Sheets on Frames, drying them hot before the Fire, then impregnating them with melted Wax, and afterwards coating them with Tinfoil. This another ingenious Friend has try’d, and as he writes me it succeeds.
The same (Mr. Henley) has invented an Electrometer which seems useful. I send you a Draft of it. It shows in what degree a Bottle is charg’d, that is, whether half, three quarters, &c. So that knowing the Force of a full Charge of any Bottle or Battery, you may by this, while charging, know the Proportion you have of such Force.
Your Experiment showing that a Stroke with black Lead on Paper would conduct a Shock, was new to me. I mention’d it to some who since tell me that they also find the solid Black Lead in a Pencil conducts as well as Wire; Which indeed, (the other being true) is not to be wonder’d at. It is however the only Property of Metal Black Lead possesses, as far as we yet know it.
Mr. Canton melts Silver and Gold Wire by Electricity, not only into fine bright little Globules, but also into Spherules of Glass, some of which he has shown me by his Microscope. They were transparent, the Light passing thro’ them, and appearing in a Focus on the Paper.
| A B | An Ivory Rod, round with a Knob at the Top, 6 Inches high |
| C | A short Tin Socket, fix’d to the Prime Conductor, to receive the End |
| D | a Cork or Pith Ball, at the End of a small Ivory Arm, turning on an |
| F | a semicurcular Plane of Ivory graduated at the Edge, to mark the |
I wish I had any thing of more Importance to communicate. Business, during the Winter, takes up my time, so that I make no Experiments myself, but what I hear of I shall continue to send you. Being, with sincere Esteem, Dear Sir, Your most obedient humble Servant