I've tried in vain to track down (in print and on-line) a healthy discussion about the interchangeability of the prepositions "from" and "of" in sentences like: The boat dock is downstream of/from the dam.

I realize of can indicate possession and that from can indicate distance or location. However, the boatdock is downstream (distance and location) but is also on the dam's downstream side (possessive).

Help me sleep at night!

Brandon

Check to see is dam in the ablative or genetive case. Dam is second declension neuter so you should be able to tell the difference.

: The boat dock is downstream of/from the dam.
Hi Brandon,
The way I see it, the sleeplessness arises from the word downstream in your example, rather than from the "of/from" dilemma. I can hardly think of another word that would accept the two "prepositions" equally interchangeably. This is due to the fact that a stream moves in nature, while on the map it is just a blue band. So when showing the way to a tourist on the street, I would say downstream from, while in a report with attached map I would use of.

the ablative or genetive case

I don't understand the terminology you are using, Faldage. But I reckon this occurs because of a kind of elision - saying the whole phrase, I would have said either:
The boat dock is on the downstream side of the dam
or
The boat dock is downstream from the dam

Another, unrelated, difference in usage between "of" and "from" is in relation to the content or makeup of a product. Dorothy Sayers had a character explain this in Murder Must Advertise. The rule she quoted there is still in effect, in some form or other, in most places.

Basically, if you say that a certain jam is made of apricots, it has to be predominantly real apricots -- more than 50%, if not 100%. However, a jam made with apricots can contain two apricots in a barrelful.

Check to see is dam in the ablative or genetive case. Dam is second declension neuter so you should be able to tell the difference.


To quote the Crash Test Dummies in God Shuffled His Feet:
"Not quite sure about what you just spoke,
was that a parable, or a very subtle joke?"

In either case I need more knowledge to appreciate it. Please could you elucidate, or pat me on the head and say "Never mind, that was for the grown ups". Thanks,
Rod

"Not quite sure about what you just spoke,
was that a parable, or a very subtle joke?"

Not sure myself.

The plain text explanation (I don't do this very often so, if you wish to make sense of my posts in the future pay attention, if you don't then you're probably not reading this anyway):

The Latin preposition de, from, takes the ablative, the concept behind of requires the genitive (yes I spelled it wrong before). The Latin for dam is claustrum, -i which is 2nd declension, neuter; the genitive would be claustri and the ablative would be claustro. How you would tell which it was from looking at the dam is beyond me; therefore we must take this in some other sense.

To wit; the secret meaning:

This is probably something that will vary depending on the dialect being spoken. Some of these are the kinds of things that get huffy prescriptionists to proclaim loudly that their version is obviously superior to (or is it superior than?) any other version because their version "makes sense". In truth, ninety nine times out of ten (n)either version makes sense and it is just a matter of what the individual learned in the formative years.

Side note: A good way to decide which is correct in such matters is to flip a coin. Decide before you flip what each side means, e.g., Heads = from and Tails = of. Flip the coin and look at the result. You will then either say, "Aha! I was right all along!" or "No, no! That can't be right!" Then go with what your heart told you all along but which you didn't know until you actually flipped the coin. When you get good at this technique you will no longer need the coin.

Further side note:

There is a support group available if you start understanding me and it doesn't bother you that you understand me. There is one out there who would fit this group but doesn't feel the need for the support group. Hi Elf

Good Gawd, David ... it made sense to me.
Send address of support group ASAP.
wow

The Latin preposition de, from, takes the ablative, the concept behind of requires the genitive (yes I spelled it wrong before). The Latin for dam is claustrum, -i which is 2nd declension, neuter; the genitive would be claustri and the ablative would be claustro. How you would tell which it was from looking at the dam is beyond me; therefore we must take this in some other sense.

Thanks for the explanation, Faldage. I had got as far as trying to decline "de" into "dam" in Latin, and "der" into "dam" from German without any success.

The support group sounds an excellent idea, though I probably don't yet qualify. My sister in law gave my daughter one of those clocks which sing bird songs on the hour and was then mortified to discover there is a web based support group for people who have been given one!

Rod

Yes, I've heard of a dam that declined. The Grand Teton, wasn't it? It may not have been ablative, but it surely ablated. And whether you were downstream of it or from it, you would have also declined. Permanently.

Faldage, where's that support group - quick!

I think Rhett Butler got it right when he said, "Frankly, Scarlett, ..."

"Frankly, Scarlett, ..."

Which I think is what I was trying to say (if not so eloquently) in the first place.