3. A dike connecting the northern ends of the first two dikes with each other, and stretching across the southern part of La Gallega, to prevent the seas which sometimes break over this reef from entering the harbor. The wall between La Gallega and Lavendera will not only cut off the rough water during northerly gales, but will also effectually prevent the deposition of sand in the harbor, because the through passage to the northwest will be stopped. Passages closed by sluice gates will be formed through this wall at about low water level, so that at any time the harbor may be flushed out and stagnation prevented. 4. After the construction of the inclosing walls the harbor will be dredged out and cleared of coral to a depth of 25 ft. below low water. 5. Following these works of primary importance comes the construction of a wooden roadway from the Hornos reef to the northwestern dike. This roadway will form the south front of the harbor, and the excavated material will be deposited on the space between the roadway and the existing bottom, so as ultimately to make it a permanent work with a masonry retaining wall fronting the harbor. The land between the roadway and the city would also be reclaimed to the extent of more than 740,000 square yards. 6. The construction of wooden piers at right angles to the roadway, which would be extended to run around the harbor as trade required it, for ships to be alongside for loading and unloading. The construction of these short piers would be similar to those used in New York and other United States ports, and they might afterward be replaced by masonry if the increase in trade justified so large an expenditure. 7. The erection of a lighthouse, at or near the eastern end of the Lavendera sea wall of a second on the eastern side of La Gallaguilla reef, and of another on the west side of La Blanquilla reef. These houses will be furnished with distinctive signals to enable steamers running in before another to run with safety between La Gallaguilla and La Blanquilla as soon as the Lavendera light is seen between the other two. The width of deep water at the entrance between the Lavendera and Hornos reefs will be 1,000 ft. The estimated cost of these extensive works is ten millions of dollars, a large sum for the Mexican Republic to expend in harbor improvements at one port but it will doubtless be found a profitable investment as it will tend greatly to promote trade, and so increase indefinitely the commerce of the port. Mr. Eads' plan having been approved by the Mexican Government the work was formally commenced on the 14th of last August. Plans were also furnished by him at the request of the Government, for deepening the mouth of the Panuco River upon which is located the city of Tampico, the Gulf terminus of the Mexican central railway system.--_Engineering._ * * * * * COST OF POWER TO MAKE FLOUR.