“I decline to read into any enactment words which are not to be found there, and which would alter its operative effect because of provisions to be found in any proviso. Of course a proviso may be used to guide you in the selection of one or other of two possible constructions of the words to be found in the enactment, and show when there is doubt about its scope, when it may reasonably admit of doubt as to its having this scope or that, which is the proper view to take of it; but to find in it an enacting provision which enables something to be done which is not to be found in the enactment itself on any reasonable construction of it, simply because otherwise the proviso would be meaningless and senseless, would, as I have said, be in the highest degree dangerous.”