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yet it requires only ordinary reflection to perceive that the con- ditions in the two cases are wholly dissimilar. The engines of mail steamers are driven to their full power, at all times, and the question of coal expenditure becomes of financial importance; hence their boilers are always designed especially for economy, and the necessary space in the ship is unhesitatingly taken. To follow this line in a naval vessel, of much less length for equal power, would incur a very excessive sacrifice of hullroom over that now given. The adoption of forced draft has made it possible to obtain enormously greater evaporation from a boiler of ordinary design than was possible with natural draft, by reason of burning a much greater quantity of coal on the same grate. To do this economically, however, the heating surface, or surface of absorp- tion of the heat from the gases of combustion, must be greatly increased, which means larger or more numerous boilers. 'The designers of machinery for war-ships have carefully considered the bearing and contingencies of this feature, and have adopted as efficiently proportioned boilers as the existing conditions justify. The assumption is that the full power of this class of vessel never will be required except for short periods, when the production of it at the lowest rate of economy will not be vital; and a mean is considered advisable, where space is of such para- mount importance. 'The quality of workmanship shown in the details of construction, with its guarantee of durability, is sec- ond to none in the world. The desire of marine engineers is to produce a type of boiler which shall do away with the necessity of such enormous- ly large and heavy shells, and present a lighter substitute which will perform the duties of both envelope and heating surface conjointly. A very great reduction in size and weight is thus possible, and the numerous forms of tubulous boilers are the outcome of this desire which, year by year, is intensified by the gradual necessary increase in the proportions of the cylindrical type. Ree tiincly small diameter, and variously connected, inside. of which the water circulates, and around which a light casing of metal, lined with refractory material is built to confine the hot gases to action upon their outer surfaces. Thus the tubes be- come parts of the shell as well as continuing to be heating sur- face, and by reason of small diameters, even in the connecting drums, all very thick plates are avoided and the highest desir- able steam pressure safely carried. 'The amount of contained water is also greatly reduced as well as much more effectively disposed for evaporation than obtains in the Scotch boiler, where the water is solid bulk, much of it below all heating surface, and only brought to the boiling-point slowly or by forced circu- lation. smaller vessels, such as torpedo-boats or launches, but its adop- tion for larger ships has been delayed for reasons which, tempor- © arily at least, counterbalance the evident advantages of less weight and size, better circulation more efficient evaporation and the rapidity with which steam can be raised. One of these is that their very compactness militates against their accessibility for cleaning and examination, and it is feared that without a posibility of unusual care their decay will be rapid and their life short, when placed in the damper holds of deeper vessels, where their use will be interrupted by long periods of idleness. Besides this, the ready renewal of defective tubes is not per- fectly provided for in most designs, and many practical difficul- ties have attended this work with the smaller sizes, despite a theoretical demonstration of the ease of such operations. Es- pecially is this true after some considerable use, and indicates a probable trouble and incites caution in those who would like to abandon the bulkier but more accessible form. Experiment of course, is the only way to prove their real adaptability to the service required, and the government has placed on board the United States cruiser Monterey, just built in California, fourtubulous boilers. Much interest centers in the coming trial of these boilers, but upon the reports which shall be made by the engineers in charge, after a continuous experience with them under the various conditions of a cruise, will depend any verdict of value. The field is open still for in- ventive minds, as the perfect type has not yet been evolved. The study is in better shape now by reason of the many devices already constructed and found wanting, as their faults, as well their points of excellence, serve to aid the designer in marking his lines for improvement. Send 20 cents in stamps for Tabulated State- ment showing Lake Superior ore production for 1891, and the past 36 years. _ per cent. cent. The tubulous boiler consists of numerous tubes of com- | For years this tubulous form has found favor for use in | - tion of an elevator here. MARINE REVIEW. | : Census on Lake Fisheries. Special Correspondence to the MARINE REVIEW. WasHINGTON, D. C., June 16.--The census bureau will in a few days issue a bulletin in reference to the fisheries of the great lakes, presenting sta- tistics by which will be shown the extent of the commercial fisheries in that quarter as they existed in 1889. The returns represent over 3,500 miles of shore line canyassed by the agents of the bureau. It is stated in this bulletin that the fisheries of the great lakes are the most extensive lake fisheries in the world. \ Their great economic importance to the states adjacent to the lakes is attested by tabular statements,in which are shown the large number of persons engaged, the great amount of capital invested and the enormous quantity and value of the products taken. Nor does the importance of these fisheries stop with the mere capture and handling of fish; other industries of great extent are more or less related to, or entirely dependent upon these fisheries, among which boat and vessel building stands prominent. In 1889, 6,896 persons were engaged in the capture of fish on the great lakes. These employed 107 steamers, valued at $357,650, and 3,876 other vessels and boats worth $325,- 438, representing a total capital of $683,088 invested in lake craft. The cap- ital invested in shore property directly connected with the fisheries was $804,- 814, with a large amount invested also in the necessary fishing apparatus, in- cluding seines, nets, etc. These items all told, are a total investment in fish- ing property on the great lakes of $2,832,959. More than one-half of this total investment is to be credited to Lake Erie, which advances from second position held in 1880 to first rank in this respect, thé increase being greater than in any other lake, amounting to 187 Lake Michigan, which stood first in 1880 has dropped to second place, and shows a smaller increase than any other lake, namely 30.01 per Lakes Huron and St. Clair have advanced 160 per cent., and they are closely followed by Lake Superior with an increase of 150 per cent. Lake Ontario has declined in the amount of investment and exhibits a loss of 11.72 per cent. The aggregate net increase has been $1,486,984, or 110 per cent. Next to the more extensive employment of-improved apparatus, perhaps | nothing connected with the means and methods of fishing has contributed so much to the increase in the value of the fisheries as the introduction and gen- _ eral adoption of steam vessels by the principle firms for capturing and collect- ing. The increase in steam fishing vessels on the lakes has amounted to 118 per cent. since 1880. Management of the Welland Canal. Special Correspondence to the MARINE REVIEW. Krnaston, Ont., June 16.--The only matter of marine importance which was brought before parliament last week was by the Hon. Mr. McCallum. It was in connection with the superintendency of the Welland canal. He asked for the production of the evidence taken by the commissioner who inyes- tigated the management of the canal nearly three years ago. He said it was _ inexplicable to him why Supt. Ellis should be retained in the public service, considering the evidence that was forthcoming before the commissioners. For some reason or other the government had declined to lay the evidence before _ parliament, but if they persisted in their intention he would be compelled to read the whole of it to the senate, so that it might go on the public records. Evidently there was a power behind the throne protecting Mr. Ellis. The premier assured Mr. McCallum that the minister of Canada would inyesti- gate the whole question thoroughly during the recess. « Mr. H. Calvin, timber shipper, was elected by acclamation to represent Frontenac in parliament. He is a wealthy ship owner and a strong advocate of reciprocity in wrecking. On Thursday evening the board of trade will meet and discuss the erec- The citizens, it is understood, will offer to subscribe 40 per cent. of the stock if the forwarding companies will do the rest. Control of Dock Property at the Sault. Special Correspondence to the MARINE REVIEW. Savutt Sre. Martz, Mich., June 16.--Few vessel owners realize the fact that they are indirectly paying a toll for locking through the St. Mary's canal lock. This is especially the case with schooners. The Hursley tug line charges schooners $5 each for towing them from the government dock over to the lock, past the Union dock and the coal company's dock. This company owns 525 feet of dock frontage, which is wedged in between the government docks at the east end of the lock. If this property was owned and controlled by the government, schooners would not be compelled to get a tug to tow them to the lock. Control of the dock by the government would also prevent the danger which now exists of vessels striking tonnage which may be moored to the Union dock or coal company's dock. The time has arrived, it would seem, when it is necessary in the interest of the government as well as the vessel owners that this strip of dockage be purchased and controlled by the govern- ment. Under such control much better time could be made in the lockages. Vessel owners are at present paying for tugs aslarge a figure as canal tolls would amount to if the canal was still under control of the state of Michigan, as the canal rates were gradully decreasing when the United States assumed charge of the lock. The owners of the Union dock as well as the coal com- pany are understood to be willing to sell if satisfactory terms can be arranged. ~