The London and Birmingham Railway
Shown here are extracts of the original civil engineering records for the construction of Nash Mills (Kings Langley) and Boxmoor (Hemel Hempstead) Canal Bridges in 1836/7. These show the types and quantities of materials used at approximately monthly intervals.
Nash Mills Canal Bridge

These photographs show Nash Mills Canal Bridge in 2007. The bridge has been reconstructed in more recent times but it appears that the concrete has encased, or kept to, the original form.
Boxmoor Canal Bridge
The faint pencil writing at the bottom reads: “Diversion of Grand Union Canal, May 14 to 22, 1836, Navigators Time 2846 days at 4/6 = £640-7-0. Beer, wear & tear of Implements, Use of horses etc £121-3-0. Total £761-10-0.”
That the, presumably previously straight, canal has been slewed and diverted under the railway bridge can be clearly seen in the photographs below. It took 9 days to do this employing on average 316 navvies per day. The work had to be done quickly as the closure of the canal would have involved compensation for putting it out of use.

For Google Satellite view of the Nash Mills Canal Bridge location CLICK HERE.
For Google Satellite view of the Boxmoor Canal Bridge location CLICK HERE.