“The following table exhibits the quantity of matter (both in solution and in solid state) contained in an imperial gallon of each specimen.
“STREET WATERS.
| Number of Bottle. | Name of Street. | Quality of Paving. | Quality of Traffic. | Residue in an Imperial Gallon. | ||
|---|---|---|---|---|---|---|
| Soluble. | Insoluble. | Both. | ||||
| Grains. | Grains. | Grains. | ||||
| 1 | Duke-street, Manchester-square | Macadam | Middling | 92·80 | 105·95 | 198·75 |
| 7 | Foley-street (upper part) | „ | Little | 95·13 | 116·30 | 211·43 |
| 5 | Gower-street | Granite | Middling | 126·00 | 168·30 | 294·30 |
| 12 | Norton-street | „ | Little | 123·87 | 3·00 | 126·87 |
| 3 | Hampstead-road (above the canal) | Ballasted | Great | 96·00 | 84·00 | 180·00 |
| 4 | Ferdinand-street | „ | Middling | 44·00 | 48·30 | 92·30 |
| 2 | Ferdinand-place | „ | Little | 50·80 | 34·30 | 85·10 |
| 10 | Oxford-street | Granite | Great | 276·23 | 537·10 | 813·33 |
| 6 | „ | Macadam | „ | 194·62 | 390·30 | 584·92 |
| 11 | „ | Wood | „ | 34·00 | 5·00 | 39·00 |
“The influence of the quality of the paving on the composition of the drainage water,” says Professor Way, “is well seen in the specimens Nos. 10, 6, and 11, all of them from Oxford-street, the traffic being described as ‘Great.’
“The quantity of soluble salts is here found to be greatest from the granite matter from the macadamized road, and very inconsiderable from the wood pavement.
“The same relation between the granite and macadam pavement seems to hold good in the other instances; the granite for any quality of traffic affording more soluble salts to the water than the macadam.
“The ballasted pavement holds a position intermediate between the macadam and the wood, giving more soluble salts than the wood, but less than the macadam.
“The quantity of solid (insoluble) matter in the different samples of water, which is a measure of the mechanical waste of the different kinds of pavement, appears also to follow the same relation as that of the soluble salts; that is to say, granite greatest, next macadam, then ballasted, and, lastly, wood pavement, which affords a quantity of solid deposit almost too small to deserve notice.
“The influence of the quality of traffic on the composition of the different specimens of drainage is well marked in nearly all cases; the greatest amount of matter both insoluble and soluble being found in the water obtained from the streets of great traffic.
“The following table shows the composition of the soluble salts of four specimens, two of them being from the granite, and two from the macadam pavement.