I received your favour of Sept. 9 and should have answer’d it sooner, but delay’d in Expectation of procuring for you some Book that describes and explains the Uses of the Instruments you are at a loss about. I have not yet got such a Book but shall make further Enquiry. Does not Desaguliers in his Course explain them? You do not mention the Reasons of your being tired of your Situation in the Academy. And if you had, it would perhaps be out of my Power at this Distance to remedy any Inconveniences you suffer or even if I was present. For before I left Philadelphia, everything to be done in the Academy was privately preconcerted in a Cabal without my Knowledge or Participation and accordingly carried into Execution. The Schemes of Public Parties made it seem requisite to lessen my Influence whereever it could be lessened. The Trustees had reap’d the full Advantage of my Head, Hands, Heart and Purse, in getting through the first Difficulties of the Design, and when they thought they could do without me, they laid me aside. I wish Success to the Schools nevertheless and am sorry to hear that the whole Number of Scholars does not at present exceed an hundred and forty.

I once thought of advising you to make Trial of Your Lectures here, and perhaps in the more early Times of Electricity it might have answer’d; but now I much doubt it, so great is the general Negligence of every thing in the Way of Science that has not Novelty to recommend it. Courses of Experimental Philosophy, formerly so much in Vogue, are now disregarded; so that Mr. Demainbray, who is reputed an excellent Lecturer, and has an Apparatus that cost nearly £2000, the finest perhaps in the World, can hardly make up an audience in this great City to attend one Course in a Winter.

I wonder your roughening the Glass Globe did not succeed. I have seen Mr. Canton frequently perform his Experiments with the smooth and rough Tubes, and they answered perfectly as he describes them in the Transactions. Perhaps you did not use the same Rubbers.

There are some few new Experiments here in Electricity which at present I can only just hint to you. Mr. Symmer has found that a new black Silk Stocking worn 8 or 10 Minutes on a new white one, then both drawn off together, they have, while together, no great Signs of Electricity; i.e. they do not much attract the small Cork Balls of Mr. Canton’s Box; but being drawn one out of the other, they puff out to the full Shape of the Leg, affect the Cork Balls at the Distance of 6 Feet and attract one another at the Distance of 18 inches and will cling together; and either of them against a smooth Wall or a Looking Glass, will stick to it some time. Upon Trial, the black Stocking appears to be electris’d negatively, the white one positively. He charges Vials with them as we us’d to do with a Tube. Mr. Delavall has found that several Bodies which conduct when cold, or hot to a certain Degree, will not conduct when in a middle State. Portland Freestone, for Instance, when cold, conducts; heated to a certain degree will not conduct; heated more it conducts again; and as it cools, passes thro’ that Degree in which it will not conduct till it becomes coller.

This with what you mention of your Cedar Cylinder, makes me think, that possibly a thin Cedar Board, or Board of other Wood, thoroughly dried and heated, might if coated and electrified, yield a Shock as glass Planes do. As yet I have not try’d it.

But the greatest Discovery in this Way is the Virtue of the Tourmalin Stone, brought from Ceylon in the Indies which being heated in boiling Water, becomes strongly electrical, one side positive, the other negative, without the least Rubbing. They are very rare but I have two of them and long to show you the Experiments.

Billy joins with me in Compliments to you and to good Mrs. Kinnersley and your promising Children. I am with much Esteem and Affection Dear Sir, Your most obedient Servant.