From Michael Faraday   22 November 1853

My dear Henslow

1 cubic inch of Water weighs –––––––––– 252.458 grams

–––––––––––– oxygen –––––––––––––– 0.3438

–––––––––––– hydrogen –––––––––––– 0.021483

–––––––––––– 2 vols hy & 1 vol oxygen – 0.128922

252.458/0.128922 = about 1958

So 1958 vols of mixed O & H make 1 vol of water and therefore your middle line of 1:2 gives or requires 1/653 in the water column. The g as equivalent for water is right i.e. the g which you have ? opposite 0 1. [figures drawn in cylinders] is right

Ever truly yours | M. Faraday