THE COLOSSAL, overwhelming, mammoth size of Harvard's library system is a well-documented fact. Tour guides comment on it every day. Eleven million volumes overall. Five miles of bookshelves in Widener alone. In other words, big.

What the tour guides don't like to mention, however, is just how fundamentally strange the country's oldest library system happens to be. Indeed, the just-plain-weirdness of the University library is as impressive, in a way, as its immense size.

This weirdness does not have to be explained to anyone who has ever stood and listened to the "drip-drip-drip" that rains eternally down in the passageway between Widener and Gov. Docs. Where does all that water come from? And where is it going? Is any of it getting on the books?

It's questions like these that make a trip to Widener an experience to be cherished. Most of the library's oddities have to be seen to be believed. But a few merit special attention. Herewith a few examples:

POINT 1. HOLLIS terminals. Why are there none inside the stacks? The current setup presumes that all library users can develop a detailed and comprehensive research plan while sitting in the comparative safety of the reference room.

I am sure that there are people at this University organized enough to work out such a plan. I am not one of them. I am not sure I have ever even met one of them. I think of new things I want to look for when I am wedged between two of the movable stacks on the third level of Pusey--P3, as the library cognoscenti know it. Then I have to trek all the way back to Widener circulation to find a HOLLIS machine.

A similar problem exists with the library's ever-elusive Xerox machines, all of which are exactly 15 minutes away from everything that one might conceivably want to photocopy. It might make some sense to put Xerox machines over by the noncirculating periodicals and journals in the Widener stacks.

POINT 2. Change. Not the earth-shaking kind advocated by our crusading campus revolutionaries, but the loose kind which is almost nowhere to be found in the Widener-Pusey-Lamont system. Where on earth is one supposed to get it? Sure, there are change machines over by the Xerox machines. But they only take $1 bills.

Suppose--hypothetically, of course--that you are trying to photocopy a periodical in Lamont, but that the only cash you have is a $5 dollar bill. If I were ever in such a situation, it might occur to me to try to get change from the folks over in Gov Docs, right down the stairs. Just to see what would happen, I stopped by Gov Docs the other day to see if they could break a five.

I was told that I had to go to the photo department in Widener--the only place in the entire complex authorized to make change. Unfortunately, the passage from Gov Docs to Widener goes only one way--the wrong way.

It's not so bad, I was told. "You have to go up, go down, go back and go across. Or just go outside."

Nothing to it. I bet you guys get this question a lot.

"At least four times a day--and that's just the nine-to-five shift. Better make it six times a day. During peak hours it's worse."

Adding to the problem, of course, is that the three libraries have different hours. Widener is open until 9:45 on weeknights. Lamont is open until one. Even assuming that a physical route of access to the photo desk existed, it would only be possible to use it during certain hours of the day.

One solution to this problem would be to install a system of magnetic cards similar to that used at the Office of Information Technology and the city's Registry of Deeds. But I'm not holding my breath.