It isn't clear from the text - however, it is likely that the 'recording secretary' would NOT be sitting in the back, as they would be part of the official staff of the committee and would be sitting near the President and members so they could clearly see and hear what was happening, given that it was their job to record proceedings. "Visitors from the press corps" and 'press corps' are the same thing here, i.e. some members of the press corps are present. It is these people who are sitting in the back gallery.