This JOURNAL, the official organ of the Washington Academy of Sciences, aims to present a brief record of current scientific work in Washington. To this end it publishes: (1) short original papers, written or communicated by members of the Academy; (2) short abstracts of certain of these articles; (3) proceedings and programs of meetings of the Academy and affiliated Societies; (4) notes of events connected with the scientific life of Washington. The JOURNAL is issued semi-monthly, on the fourth and nineteenth of each month, except during the summer when it appears on the nineteenth only. Volumes correspond to calendar years. Prompt publication is an essential feature; a manuscript reaching the editors on the second o the seventeenth of the month will ordinarily appear, on request from the author, in the next issue of the JOURNAL.

Manuscripts may be sent to any member of the Board of Editors; they should be clearly typewritten and in suitable form for printing without essential changes. The editors cannot undertake to do more than correct obvious minor errors. References should appear only as footnotes and should include year of publication. Ilustrations will be used only when necessary and will be confined to text figures or diagrams of simple character. The editors, at their discretion, may call upon an author to defray the cost of his illustrations, although no charge will be made for printing from a suitable cut supplied with the manuscript.

Proof-In order to facilitate prompt publication no proof will be sent to authors unless requested. It is urged that manuscript be submitted in final form; the editors will exercise due care in seeing that copy is followed.

Authors' Copies and Reprints.-On request the author of an original article will receive gratis ten copies of the number containing his contribution and as many additional copies as he may desire at ten cents each. Reprints will be furnished at the following schedule of prices:

Covers bearing the name of the author and title of the article, with inclusive pagination and date of issue, will be $2.00 for the first 100. Additional cover $1.00 per 100.

As an author will not ordinarily see proof, his request for extra copies or reprints should invariably be attached to the first page of his manuscript. The rate of Subscription per volume is..

Semi-monthly numbers..

Monthly numbers....

$6.00*

.25

.50

Remittances should be made payable to "Washington Academy of Sciences," and addressed to the Treasurer, R. L. Faris, Coast and Geodetic Survey, Washington, D. C.

European Agent: William Wesley & Son, 28 Essex St., Strand, London. Exchanges. The JOURNAL does not exchange with other publications. Missing Numbers will be replaced without charge, provided that claim is

made within thirty days after date of the following issue.

* Volume I, however, from July 19, 1911, to December 19, 1911, will be sent for $3.00. Special rates are given to members of scientific societies affiliated with the Academy.

THE WAVERLY PRESS

BALTIMORE, U. S. A.

RADIOTELEGRAPHY.-New method of using contact detectors in radio measurements. L. W. AUSTIN, U. S. Naval Radio Laboratory.

For many measurements in radiotelegraphy it is necessary to use a radio frequency-current indicator of known resistance. If the current to be measured is small it is generally customary to use a thermoelement and galvanometer. The most sensitive thermoelements are either of the vacuum type or the welded tellurium type. The vacuum thermoelements can be obtained of any desired resistance and are very sensitive but are slow in action and frequently show a bad zero drift. In addition, the deflection usually shows considerable divergence from the current-square law. The tellurium platinum elements are quick acting and follow the current-square deflection law with sufficient accuracy for all practical purposes. They are however so fragile and difficult to manufacture and transport that no manufacturer has yet undertaken to supply them commercially. It is also impossible to make the contact resistance much less than 10 ohms. It is to be noted that the resistance in both the vacuum and tellurium types changes considerably with the amount of current flowing.

On account of the difficulties mentioned, the sensitive thermoelements in our laboratory have been replaced, for the most part, by a shunted contact detector circuit arranged as shown in figure 1. Here LC is any oscillating circuit having inductance and