Letters Received to H.H. Barker, March 12, 1929

MAR 131929 TREASURY DEPARTMENT UNITED STATES PUBLIC HEALTH SERVICE OFFICE OF INDUSTRIAL HYGIENE WASHINGTON, D. C. AND SANITATION Room 1-123, "C" Bldg 16 Seventh St., S. W. March 12, 1929 Mr. H. H. Barker, Vice President, United States Radium Corpn. 535 Pearl St, New York, N. Y. Dear Mr. Barker: Thank you for your kind letter of March lst. Dr. Flinn recently wrote to Dr. Thompson in regard to lending us the Wulf electroscope which he has been using in New York. On receipt of your letter of March lst I sent him a copy of your letter, and he will probably communicate with you. I note what you say about lending us this instru- ment, and also the one which you are importing, and I ap- preciate your kind offer of help. We are going to order a Wulf bifilar electroscope from Gunther and Tegetmeyer but have not definitely decided what type we will get. As you know, there is the original Wulf type and then there is the Hess modification, and then there is a still further modification by Kolhoester, Apparently the last type which was designed for measuring the penetrating radiation of the atmosphere is the most sensitive and reli- able instrument. The Hess type is described in the Physikalische Zeitschrift for 1913, page 1135, and the kolhoester type is described in the Zeitschrift fur Physik for 1921, Band 5, page 107. As I understand it, the type which you are using is the Hess type. Would you kindly tell me what type instrument you have ordered from Gunther and Tegetmeyer? Would you also tell me