Panama Canal, Executive order [amending civil service rules relating to entire classified service so as to except from examination all officers and employees in Federal service upon Isthmus of Panama, except those who are to perform duties of clerk, bookkeeper, stenographer, typewriter, surgeon, physician, trained nurse, or draftsman, excepting from examination appointments to clerical positions on Isthmus of Panama paying not more than $75 in gold per month, and revoking similar provision applying to Isthmian Canal Commission].