July 4th, 1899 letter from Nikola Tesla to George Scherff

Colorado Springs, July 4, 1899

Dear Mr. Scherff, 

We want as soon as possible four sizes of this little instrument completed in annexed sketch, and there ought to be two pieces of each size, that is, eight pieces in all. These pieces are to go on the clockworks as Mr. Uhlman will surely understand. In order to enable as many experiments as possible to be performed we want furthermore various lengths of glass tube so as to vary the distance of the metallic plugs which will close the tube. I would like to have for each size tubes of such length, that the distance of the metallic surfaces in the glass will be, respectively 1/8", 1/4", 3/8", and 1/2", and as some of the tubes might break, it would be necessary to have at least two, but better still, three of each length. Assuming you give us two, this would make for each size of instrument 8 tubes (4 pairs of lengths specified). Now, since of each instrument there will be a pair (as nearly as possible alike), we shall want 16 tubes for each size of this device. The four sizes will be such that D will be respectively; 1/4, 1/2, 3/4, and 1". As these instruments are to be driven-by the clockworks you have sent or are sending, they want to be as light as practicable. Mr. Uhlman should see to improve some details of the sketch while keeping sizes. The space between the outer surface of the glass tube and the inner surface of this brass tube should be about 1/16". The outer tube with its plug must be of one piece as it is going to be heated and might fall apart if soldered. The part c of plug b, upon which a brush is to make contact, as usual, should be long enough to project out even then, when the smallest length glass tubes is placed inside of outer tube a. I would like to have the inner surfaces of the plugs of silver; this may be easily accomplished by either brazing or riveting silver sheet on the surfaces and finishing afterward. Polish surfaces very highly. There should be no hole anywhere as the inner chamber must be air tight, after the tubular space up to the rim k is filled with melted sealing wax (we shall do this here). Mr. Uhlman may vary any insignificant detail, but the sizes should be as asked for. For example, the part c may be screwed in the plug b, but I would not advise it, but rather make different plugs. The plugs should fit well in the glass tubes. The part e should be made to the standard, and I hope that Mr. Uhlman has made and preserved a reamer for the hole. I am in great hurry for these pieces and furthermore I want Nickel (filings). These ought to be made in degrees of various coarseness, but by tools, so that they shall be of as uniform size and shape as possible. I rely on Mr. Uhlman's resources. We made some many times before but I do not know whether he has been with me at that time. They were then made in various ways with milling tools, shears, etc., but they were always of equal size as nearly as possible. Nickel wire (thin), cut in lengths such that the pieces will be nearly small cubes, would be fairly good. But best would be to have them almost like shot. The largest pieces should not be more than 10/1000" (I me an enough for all instruments} prepared of various sizes - from very fine milling chips to the coarser grades. I tried some time ago to have small grains of aluminum wire pretty round (best would be quite round) nickel plated, but I could not find anybody to do it. Perhaps you may be more fortunate. 

Push this work through as quickly as possible, as I am preparing myself for the plant at Nantucket (for the government), and want to have as much work done as possible before I return.

I shall send instructions for new clockworks and when you get them rush them through at any price. All work must be done first class. Tell Mr. Uhlman not to lose sight of this.

Please send me Mascart and Joubert works - magnetism (or some little like this) - a large work. Also a popular work on astronomy.

We are getting messages from the clouds one hundred miles away, possibly many times that distance. Do not leak it to the reporters.

Yours sincerely,
N. Tesla