Towards the River South Esk
The B704 is a short B-road in east Midlothian.
It starts on the A768 (former B703) in Lasswade. The road heads south, climbing out of the North Esk Valley into Bonnyrigg, where it runs along the High Street before crossing the A6094 at traffic lights. It then continues southeast through town, descending as it goes, before crossing a roundabout on the B6392 Bonnyrigg bypass.
Now more-or-less in open country, the road passes an isolated church before crossing a stream and then the River South Esk. It then skirts an industrial estate to reach the A7. This is crossed at traffic lights, putting the road out of zone. The road then heads southeast along a straight, largely residential road into Gorebridge, where it zigzags over the Waverley Line before ending on the B6372, where that road has to TOTSO.
The B704 reached Penicuik in 1932
Originally, the B704 followed the strict 1922 classification rules and only existed west of the A7. However, it appears that it was soon extended out of zone. The map to the left shows that the B704 had been extended west to Penicuik (presumably ending on the A766) by 1932 and it makes sense that the B704 took on the road through Gorebridge (which is not labelled) rather than having a long multiplex along the A7.
This extension did not last that long, however, as the road from Gorebridge to Penicuik became the B6372 in 1935, cutting the B704 back to its current length.