I recognised the stamps illustartion having seen it in OMMMW Part 6; I only repeated the (rather inadequate) reference that Bick gave. Smiles' works went though many editions and his Lives of the Engineers wound up a multi-volume set as successive editions included more and more engineers. My local library only has an early edition that limits itself to the railway engineers so I'm in the same position as you.
My comment about different styles suggesting different engravers was based on my impression that the stamps engraving had a different feel to it compared to the other engravings.
Leitch had a huge output of views from all around the UK and all around the world. Clearly, like many other engravers, much of his work was based on other people's original drawings / watercolours / photos, and very likely he, like other successful engravers, employed assistants to engrave the repetative simple parts - the only way he could have realistically churned out numerous engravings to tight deadlines for illustrated journals like the 'Illustrated London News' (which he produced engravings for).
The dramatic exaggeration mentioned by Wheal is perfectly normal for the mid C19 (Leitch was at his peak in the 1860s I think) when fevered Victorian imaginations ran a perfect riot, turning Snowdonia into Alpine peaks, etc. I've a great postcard (but no scanner - sorry) entitled 'Victorian artist at work' that shows an artist working on a canvas depciting precipitous peaks, dramatic mountain torrents and menacing clouds with an early moon lowering from behind them, whilst his easel is set up in a gently rolling bucolic landscape with a babbling brook and some docile sheep in the middle distance. It really does sum up the transformations that some artists effected on the landscapes they depicted!