June 10th, 1899 letter from Nikola Tesla to George Scherff #2

Colorado Springs, June 10th, 1899

The distance between fine point and edge should be as small as possible without touching. The small platinum sheet in cutaway is shown so that by a small springing apart of the iron cores the distance between the two platinum terminals will be increased a little - same time there should be a small vibration of the wires without the pointed terminal increasing the distance like this.

The point must be very fine or polished and also the edge distance smallest possible otherwise the device would be worthless. It would be worthless if the wires would touch.

Process of Manufacture - first make steel piece very smallest size possible, fix then on the platinum, tap holes for reception of soft iron wires. Now the glassblower will furnish the piece up to line X-X, where the tube will be cracked off straight. Now Mr. Mayer can finish the wires and fix the points with platinum terminals as indicated, and when he's adjusted everything, first the glassblower will put on the seal off tube, joining it on line X-X, being careful not to spoil anything. The wires (iron wires) should be about 1/32'' thick so that they will just slightly tremble when shaken. We can now process tubes by exhaustion, not very high bubbles must. still show on the pump for a length of 1/2" on top of the mercury, not lower down. Two of the tubes could be exhausted higher than this but still the pump should show bubbles, though very small. I propose to call Mr. Wagner to finish the pieces in our room. If he can not do it then ask Mr. Greiner. Please put this through at once, and telegraph on receipt of this.

Yours sincerely,
N. Tesla
 

 We want also a fibre spool like this for the tubes to be put in. The terminals on bottom opposite each other. The fibre spool shculd be as long as practicable, but when the glass tube is inserted, the terminals ++ should stick out so as to be visible. We shall want the spool here. Please hurry up with this and send on.