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No. 62. Kalamazoo, Mich. Sept. 26, '03.

There is one point about the closed-circuit cell described in the July, '03, number, which bothers me. When the Caustic Potash solution is put into the inside of the wire gauge cylinder it will leak through the gauge and mix with the filings. Is this detrimental to the cell or not?

R. H. W,

It is necessary that the electrolyte Caustic Potash solution reach the iron filings, otherwise there would be but little action.

No. 63. Evanston, III. Oct. 8, 1903.

I am building a canoe after the model described in the April number of Amateuk Work, and would like information on a point which does not seem quite clear to me. Are the longitudinal strips to which the ribs are bent, intended to be removed before putting on the sheathing?

P. B

The long ribbands are to be removed before putting on the sheathing of the canoe. They are used simply as guides for setting up the ribs to the correct lines, this being an easy yet satisfactory way for doing this part of the work.

No. 64. Monterey, Cal. Oct. 12,1903.

Will you please tell me of a book giving the best instruction on the operation and construction of Gas or Gasoline engines. And also please state what is the best book on the Steam engine for a beginner.

C. F

A good book on the Steam engine is by Ripper, Gas and Gasoline Engines, Roberts Gas Engine Handbook. A series of articles on the subject of " Gas Engines " will begin in the next issue of this magazine.

No. 65. PIttsfield, Mass. Oct. 14, '03.

I have a few questions I wish you would be kind enough to answer in your correspondence column. I have made the Wims-hurst machine described in your paper a year ago last spring, and think it a success. Very often I draw a spark almost five inches long. I think I will make the large Wimshurst machine described some time ago and the mercury air pump described a few months ago if you think I could make a X-ray outfit? A. Would the expense be great besides the air-pump and large static machine? B. If possible could you publish an article on the X-rays. C. What is the amperage of the bichromate plunge battery described in No. 7 of Vol II with the cells in series if the voltage is 12.6. D How long will the electrolyte last? E Will it run the motor described in No. 5 of Vol. I at its full capacity?

I also got the idea of a gramaphone from your paper, I did not follow the exact lines on the sound-box or case but the clearness and volume of sound is about as good as I have ever heard on the best of machines.

W. G

A. The question is not very explicit. The expense of an X-ray outfit, except the tube, is small.

B. An article onX-ray work will be published in the near future.

C. 4. 2 amperes.

D. The electrolyte should last at least 100 ampere hours on closed circuit, but depends to a considerable extent upon the quality of the materials used in its construction.

4. This battery is more than sufficient to run the motor mentioned ; one of three cells being quite adequate.

No. 66 Minco, I. T. Oct. 18, '03.

A. I wish to know why a gravity battery will not run an elec trie motor? B. Can you tell me of any book on electrical con struction, the price, and where it can be purchasedM. B. W

A. A gravity battery will run a motor if a sufficient number of cells are emyloyed. The chief difficulty with this type of cell is the high internal resistance, and since they have an E.M. F. of only 1 volt, the amount of current is necessarily very small from one cell. A battery of 10 of these cells should be sufficient to supply the necessary current for operating small motors. Their chief advantage lies in their constancy.

B. It will be necessary to know more definitely the kind of constructive electrical work in which you are interested, before this question can be answered.

No. 67. Lynn, Mass, Oct. 3,1903.

I would like to make a jump spark coil for a 3 H. P. engine. Can you give .me information relating to the winding of the secondary coil.

J. M. H

A description of a spark coil for engines of about the size you mention is in preparation and will be published, if ready, in the next number of this magazine.