Before leaving this interesting subject of ocean oil transportation, I should like to emphasize the distinct step forward which is marked by these latest oil tankers. To-day, we have entered the era when oil fuel has passed its experimental stages and become one of the greatest boons to those associated with the navigation of the seas. The ease with which oil fuel is handled is remarkable, for vessels of the largest size--that is, those using oil instead of coal for power purposes--could replenish their stores within a few hours at any oil port. In the transport of petroleum by the modern tankers, the taking on board of a full cargo is accomplished in about a single day, thanks to the most improved means of pumping oil from the shore tanks through flexible pipes. The great oil tankers trading between this and other countries and Mexico, load up off the Mexican coast by means of a submarine pipe-line, and, reckoning but fourteen return trips per annum, it will easily be apparent what immense stores of petroleum can with ease be brought to the centres of consumption. Compare this with the primitive methods of transport in barrels, and it will be readily seen with what rapidity the hands of progress have moved during comparatively recent years. The vast majority of oil tankers to-day, true to their calling, derive their power from oil, for they burn it under their furnaces, and, therefore, are not liable to those tedious delays so inseparable from the use of coal, and should severe storms beset their passage in Mid-Atlantic, then a little oil pumped overboard will quell the most turbulent sea and permit a safe passage onward. It is evident, however, that the motor-engined oil tanker will be the order of the future, for already vessels are being built which utilize oil fuel internally--a much more economical process than burning it under boilers. CHAPTER VI PETROLEUM AS FUEL So much has been written of late as to the use of petroleum as fuel for the purposes of steam-raising, that the reader is bound to be more or less _au fait_ with the subject. It is, of course, one of vast importance, and during the next decade is certain to receive far more consideration than it has hitherto done, owing to the general desire that our coal wealth shall be conserved as much as possible. Given the one allowance that oil fuel can be procured at anything approaching a reasonable figure--and there is no reason why, in normal times, this reasonable price should not be prevalent all over the world--then petroleum offers many advantages over its older competitor, coal. The ease with which large quantities can be handled, the simple method of operating anything which is fired by petroleum as fuel, and the fact that its heat-giving units are far higher than those of coal, will ever be the chief factors governing its popularity.