"in the Beaume (don't think the acute accent will travel by e-mail)
hydrometer system , for liquids heavier than water
0 degrees equals a specific gravity of 1,
1 degree equals 1.007,
2 degrees equal 1.013,
3 degrees equal 1.02
and so on (it says).
For liquids lighter than water ,
10 degrees equal 1
and for every rise of 1 in the degrees ther is a drop in the specific
gravity or about .005"
Cassell's Cyclopaedia of Photography
Well, isn't that just crystal clear!
Peter Marshall
Fixing Shadows and elsewhere:
http://faraday.clas.virginia.edu/cgi-uva/cgiwrap/~ds8s/Niepce/peter-m.cgi