Among, the city's manufactures are refined oil, Portland cement, vitrified brick and tile, glass, asphalt, ice, cigars, drilling machinery, and flour.
For a long period the city was noted for its commerce with the West Indies, which began to decline about 1876, but the coast trade and commerce with Great Britain are still considerable, especially in the winter, when Portland is the outlet of much of the trade from the Great Lakes that in the other seasons passes through Montreal.
At one time Portland cement concrete was considered to be lacking in fireproof qualities, but now it is regarded as one of the best fire-resisting materials known.
It will be observed that in the hydration of tricalcium silicate, the main constituent of Portland cement, a large portion of the lime appears as calcium hydroxide, i.e.
In 1653 Deane was with Blake in command at the battle off Portland and later took the most prominent and active part in the refitting of the fleet on the reorganization of the naval service.
The hilly peninsula, to which Portland was confined until the annexation of the town of Deering in 1899, is nearly 3 m.
Professor Lester Ward has instituted a new generic name, Cycadella, for these woolly forms. In a few cases the fossil stems show no trace of any lateral flowering shoots, and in that respect agree with modern forms: an instance of this is afforded by a large Cycadean trunk discovered some years ago in one of the Portland quarries, and named Cycadeoidea gigantea (fig.
Among those who experimented in this direction was Joseph Aspdin, of Leeds, who added clay to finely ground limestone, calcined the mixture, and ground the product, which he called Portland cement.
In the neighbourhood of Glens Falls are valuable quarries of black marble and limestone, and lime, plaster and Portland cement works.
The matter was carefully investigated, and it was found that the sulphate of magnesia in the sea-water has a decomposing action on Portland cements, especially those which contain a large proportion of lime or even of alumina.