London Main Drainage: driving a tunnel at Peckham, 1861. Illustration of ...the manner in which the sewer is carried forward by tunneling instead of opening a trench...[part of the] plan now being carried out by the Metropolitan Board of Works, under the direction of Mr. J. W . Bazalgette, engineer-in-chief...the estimate was ?3,000,000 and works to the amount of ?2,000,000 have been contracted for...These contracts embrace fifty miles of main intercepting sewers, for the most part under ground; consequently but little is seen of them, and as little generally known. They are great works...requiring much more skill and care in their execution than is usual or necessary...above ground... It may, perhaps, assist our non-professional readers to form an estimate of the immense amount of work that has to be done to complete only one of these great drains if we give an approximation to the quantity of materials used in it: For the northern high-level sewer half a million yards of earth had to be excavated to form the trench in which it was constructed; 40,000,000 of bricks had to be laid with the greatest care and accuracy; 100,000 cubic yards of concrete had to be deposited to form foundations, backings, coverings, &c. From "Illustrated London News", 1861.