The volume which air or steamout of contact with waterof a given temperature acquires by being heated to a higher temperature, the pressure remaining the same, may be found by the following rule:To each of the temperatures before and after expansion, add the constant number 458: divide the greater sum by the less, and multiply the quotient by the volume at the lower temperature; the product will give the expanded volume.

They seem to think of it as a property the object acquires.