Hmm... let's see if I read it right...

(( you ARE adjusting for temperature, right? ))
[color=blue]
> 10 lbs of Maris Otter malt in 2.5 gal water produced a liquor
> reading 1.080![/color]

That's 80*2.5 = 200 sugar points.

[color=blue]
> After boiling, ... the s.g. read 1.048-- ...[/color]

If you had 5 gallons, then that is 48*5 = 240 sugar points.

The 200 and 240 is pretty close, especially since I'm guessing about
the water volumes... if either volume is different, those numbers will
probably be much closer.

Bottom line... you must consider the volume of water and the amount of
sugar you get out... using "sugar points" is the best way to do that.

((Note, you can do all kinds of math with sugar points to figure volumes
and gravities out... for example, from the initial 200 sugar points,
you can determine how many final gallons of wort you'll need for a given
gravity so you know when to stop your boil or how much water to add, ie:
If you want 1.060 FG and you started with 200 sugar points, then
you just do 200/60 = 3.3 gallons final at 1.060.
You can also use them to figure how much water you need to add post boil
to reduce your gravity to a desired point, etc.))

It could be that I'm off on a tangent... if so, please post what volumes
of water/wort you're measuring the gravity in, temperatures,
adjustments, etc...

Derric