However, this antagonism from outside craft unions, and these involuntary internal compromises with the craft-union idea were not the most serious difficulties which now beset the Industrial Workers of the World. The organization was threatened with wholesale defection and very soon actually suffered it in some quarters. During the spring of 1906 it became evident that a movement was afoot in the lumber camps of the northwest to organize the lumber workers in a general union outside of the I. W. W. Moreover, it appeared that the moving spirit in the agitation was one Daniel MacDonald--charter member of the Industrial Workers of the World from the old American Labor Union--a man who had not long since been an organizer for the I. W. W., and who must at the time have been a member of that organization, since he was sent as a delegate to the second convention. Mr. MacDonald explained the nature of the proposed organization in a letter to Mr. James Brookfield of Crescent City, California, dated at Butte, Montana, March 27, 1906. He does not mention the I. W. W. He writes that there is a movement on foot now in this state [Montana] and throughout the western country to organize a United Lumber Workers' general organization, to be composed of all men engaged in the lumber industry.... This organization is to be constructed on lines broad enough and having sufficient scope to meet every essential requirement of the men engaged in the lumber industry, and to give them general support, uniform benefits and the universal respect and protection so woefully needed.[192] The attempt was not successful. The lumber industry was destined to be one of the most fertile fields for the propaganda of the I. W. W. and to be one of its most solidly established divisions. This disloyal agitation on the outside in 1906 was a comparatively insignificant movement. It merely deprived the organization of a few individual members, and delayed somewhat the I. W. W. invasion of the lumber industries. The most serious defections occurred in the Metals and Machinery, and the Mining Departments. The former department at the outset comprised two groups of metal workers: the United Metal Workers International Union and the Amalgamated Society of Engineers. The United Metal Workers had been a part of the American Federation of Labor until shortly before the first I. W. W. convention, and was on its adjournment installed as a part of the Metals and Machinery Department of the I. W. W. The Amalgamated Society of Engineers had also been a part of the American Federation of Labor.