isia.J 



THE CIVIL ENGINEER AND ARCHITECTS JOURt^AL. 



27 7 



Tabi-e VI. — Showini/ the Actual Duty, and that which is theoretically 

 possible, of the Coals examined. 



* Practical. f Theoretical. t Calculated from heat obtained. 



To ascertain how far our boiler was inferior to Cornish boilers, 

 as principally from its size and less efficient coating it was likely 

 to prove, we requested Mr. Phillips to make some experiments on 

 one of the best engines in Cornwall. It was found by these e.^pe- 

 riments, that 11-42 lb. of water were evaporated by every pound of 

 Welsh coal corresponding in composition to that of Mynydd 

 Newydd ; or, in other words, that improved Cornish boilers on a 

 large scale may be assumed to have a superiority of nearly 20 per 

 cent, over that used in these e.xperiments. As the results stated 

 in this Report are only relative, the comparison is not affected by 

 this difference. 



We have anxiously looked to the application of these experi- 

 ments to the different varieties of patent fuel, but we have not 

 been able to carry our observations in this direction to the extent 

 we could have desired, from our inability to procure patent fuels 

 in sufficient number, although our applications to the patentees 

 have been numerous. Three varieties have been already examined, 

 viz., those manufactured under the patents of Messrs. Wylam, 

 Warlich, and Bell, and the results are given in the tables. The 

 varieties of patent fuel are generally made up in the shape of 

 bricks, and are therefore well adapted for stowage ; so that, 

 though the specific gravity of patent fuels is lower than that of 

 ordinary coals, from their shape and mechanical structure there 

 are very few coals which could be stowed in a smaller space per 

 ton. While we look to the different varieties of patent fuel as of 

 tlie highest importance, and, from their facility of stowage, as 

 being peculiarly adapted for naval purposes, and perhaps even 

 destined to supersede ordinary coal, at the same time, the greater 

 part do not appear to be manufactured with a proper regard to the 

 conditiong required for war steamers. It is usual to mix bitumi- 

 nous or tarry matter with bituminous coal, and from this compound 

 to make the fuel. An assimilation to the best steam coal would 

 indicate, however, the very reverse process, and point to the mixture 

 of a more anthracitic coal with the bituminous cement. As the 

 greater part is at present made, it is almost impossible to prevent 

 the emission of dense opaque smoke, a circumstance extremely in- 

 convenient to ships of war, as betraying their position at a' dis- 



tance at times when it is desirable to conceal it. Besides this and 

 other inconveniences, the very bituminous varieties are not well 

 suited to hot climates, and are as liable to spontaneous combustion 

 as certain kinds of coal. To avoid these inconveniences, some 

 kinds of patent fuels have been subjected to a sort of coking, and 

 thus, in a great measure, obtain the desired conditions. There is 

 little doubt, however, that notwithstanding the large number of 

 patents in operation for the manufacture of fuel, its value for the 

 purposes of war steamers might be much enhanced by its prepa- 

 ration being specially directed to this object. It will be seen, by 

 reference to Table II., that the tbree patent fuels examined rank 

 among the highest results obtained. Should it be desirable to 

 continue this inquiry, i(e conceive that it would be advantageous 

 to pay special attention to this subject, by experimenting upon 

 proper mixtures of different coals. Even anthracite may be in- 

 troduced into such mixtures with advantage. 



It is of much importance in an economical inquiry on coals, to 

 obtain exact information as to the effects likely to be produced 

 upon them by stowage and continued exposure to high tempera- 

 ture, not only as regards their deterioration, but also as to the 

 emission of dangerous gases by their progres.sive changes. 



The retention of coal in iron bunkers, if these are likely to be 

 influenced by moisture, and especially when by any accident 

 wetted with sea-water, will cause a speedy corrosion of the iron, 

 with a rapidity proportionate to its more or less efficient protection 

 from corroding influences. This corrosion seems due to the action 

 of carbon or coal forming with the iron a voltaic couple, and thus 

 promoting oxidation. The action is similar to that of the 

 tubercular concretions which appear on the inside of iron water- 

 pipes, when a piece of carbon, not chemically combined with the 

 metal, and in contact with saline waters, produces a speedy corro- 

 sion. Where the " make" of iron shows it to be liable to be thus 

 corroded, a mechanical protection is generally found sufficient. 

 This is sometimes given by Roman cement, by a lining of wood, or 

 by a drj'ing oil driven into the pores of the iron under grent 

 pressure. 



Recent researches on the gases evolved from coal, prove that 

 carbonic acid and nitrogen are constantly mixed with the inflam- 

 mable portion, showing that the coal must stiU be uniting with 

 the oxygen of the atmosphere, and entering into further decay. 



Decay is merely a combustion proceeding without flame, and is 

 always attended with the production of heat. The gas evolved 

 during the progress of decay, in free air, consists principally of 

 carbonic acid, a g.is very injurious to animal life. It is well known 

 that this change in coal proceeds more rapidly at an elevated tem- 

 perature, and therefore is liable to take place in hot climates. 

 Dryness is unfavourable to the change, while moisture causes it to 

 proceed with rapidity. M'hen sulphur or iron pyrites (a compound 

 of sulphur and iron) is present in considerable quantity in a coal 

 still changing under the action of the atmosphere, a second 

 powerful heating cause is introduced, and both acting together, 

 may produce what is termed spontaneous combustion. The latter 

 cause is in itself sufficient, if there be an unusual proportion of 

 sulphur or iron pyrites present. 



The best method of prevention, in all such cases, is to ensure 

 perfect dryness in the coals when they are stowed away, and to 

 select a variety of fuel not liable to the progressive decomposition 

 to which allusion has been made. This is, however, a subject of so 

 much importance to the steam navy, that it continues to receive 

 our careful attention ; and, beyond these general recommendations, 

 it would be premature to offer any decided course for adoption, 

 from the present limited series of observations. 



Several varieties of coal were transmitted from Formosa and 

 from Borneo, for analysis, the results of which are contained in 

 the accompanying table. The quantity of each kind was so small, 

 that no experiments could be made on their evaporative value. 

 We extract from the preceding table the following results : — 



