District 10a is all that portion of Siskiyou and Modoc Counties which is described as follows:
Beginning at the intersection of west longitude 122 degrees 10 minutes with the Oregon-California boundary line, thence southerly along said line of longitude to north latitude 41 degrees 30 minutes, thence easterly along said line of latitude to the point where it intersects west longitude 121 degrees 10 minutes, thence northerly along said line of longitude to the Oregon state line, thence westerly along said state line to the point of beginning.