Amid the discussions on the steam communication question, following upon the movement recently made in England to obtain the establishment between Sydney and Singapore, the application of steam navigation to the direct sea course by the Cape of Good Hope has not been considered. In the present position of the question, it maybe advisable to limit , our expectations and exertions to the attainment of the lesser scheme, as affording the readiest means of effecting the object of rapid mail packet communication, leaving the greater and more important establishment to future commercial enterprise, and progressive advances of the science. Such being the present feature of the subject, any prolonged delay in carrying out the Indian extension will be regarded with dissatisfaction. New South Wales has come pre-eminently forward by offering her aid towards the maintenance of the projected undertaking via Torres Straits to Singapore, and has temporarily laid aside the claims of the Australian colonies to a separate mail packet establishment, is the expectation of more immediately reaping the benefit of quick postal communication by a Junction with the existing line to China. The colonists naturally presume that they are now on the eve of obtaining this desirable communication ; and may still hope that the establishment of the commercial route, by which the conveyance of goods and passengers from England can be effected as rapidly as the mails overland, will also in due time be carried into effect.

Every practical advance, as well as actual improvement in steam navigation, is a step towards the fulfilment of the latter project ; therefore the recent arrival of H.M. steam sloop Inflexible in the harbour of Port Jackson from Devonport and the Cape of Good Hope, has been regarded with peculiar interest - the first voyage approaching to the character of a steam passage to Australia having been effected by this steamer, and with highly satisfactory results. This vessel, the inspection of which during her stay in our harbour, afforded no small gratification to numbers of our fellow citizens, as exhibiting to them for the first time various improvements in the formation and application of the marine steam engine attained of late years, will, by her arrival, form an epoch in colonial history, and by the performance of her voyage mark an era in the progress of navigation by steam. Ever since the successful voyage of the Great Western on the Atlantic , the practicability of reducing by one-half the present term of the voyage to Sydney, by the employment of similar vessels, has been advocated and urged : but, until the present era, all the submitted estimates were comparative theory. The Inflexible has surpassed theory in many respects, and therefore the following brief analysis and leading results of her voyage may prove interesting, and at the least highly instructive.

Allow me, to observe is the first place, that the Inflexible measures 1122 tons, and was built at Milford Haven in 1846. Her engines are of older construction, and were originally intended for another ship, as the appearance of the cylinder shafts above deck tends to show. Her two direct acting marine engines are of the nominal horse power of 375 horses, and are fitted with the expansive gear. Her four boilers are oblong shaped, with three flues to each. The engine-room is about one-half less than in the old engines ; this great saving is owing chiefly to the cranks being placed, and acting directly above the cylinders. The operation of the expansive principle is that which effects the great saving is the expenditure of fuel. As the action of the wind on the sails assists in propelling the vessel, there is, therefore, so much the less steam power required in order to maintain the necessary speed. By the plan introduced of cutting off the steam in its passage to the cylinder, and causing the piston to work expansively, this saving is effected, both simply and efficiently, and is regulated with accuracy, according to the state of the weather and the speed attained. On the passage to Australia, sufficient steam was generated by the employment of nine, and frequently only six flues out of the twelve to acquire a speed of seven to eight knots. The usual practice is to work the engine expansively, excepting when the speed is reduced to six knots - on which occasion the full steam is then applied. When the wind is strong in favour, with a moderate sea, the steam power employed on the expansive system is little more than, what may be just necessary to turn the paddles. Great facilities are afforded during the application of the expansive principle for cleaning out the boilers, which can be done in turn. without diminishing the ordinary speed, and by frequently performing it, the accumulation of sediment is prevented, thereby promoting the preservation and safety of the boilers. Coal boxes are ranged between the machinery, and sides of the vessel, and are thus made subservient to preserve the vital parts injuries more peculiar to war steamers.

The capacity of the Inflexible for fuel is 500 tons. Her large paddle-boxes, although fitted with a life-boat on each, and comprehending places for culinary and other useful purposes, are an obstruction during head winds and heavy seas. By the frequent alternate emersion and immersion of the paddle wheels, much power is lost in ocean steaming, and the application of the screw principle on this voyage is still a desideratum promising greater results. The plan of "disconnecting" has been in use by war steamers for some time, but is effected in the Inflexible on a different principle from that formerly in use, and which occupies one-tenth of the time ; it is that of the friction strap, and merely requires the turning of two screws, and striking aside the keys which connect the parts ; in order to set the paddles free of the engine.

On her departure from Devonport on the 9th of August last ; the Inflexible had 392 tons of coal is her boxes, considerably less than her quantum ; 80 tons of patent fuel intended for her use having been behind - probably in consequence of the large amount of dead weight already onboard - being not less than 150 tons, exclusive of fuel. The total weight of cargo, fuel, engines, boilers, water, stores, ammunition. &c., was estimated at 1200 tons. She then drew 15 feet 6 inches forward, and 15 feet 10 inches aft : immersion of paddle wheels 5 feet 7 inches. From the 9th to the 28th of August, the course of the Inflexible was as direct as could be taken for the Cape of Good Hope ; at the latter date she had made more than half the distance between England and the Cape ; being near the equator, in lat. 3° 44 N., lon. 13° 27 W. This point was attained in a period of eighteen days sixteen hours, at an average speed per diem of 179 nautical miles, or 7½ knots per hour, being 3345 miles by the log, and direct course 3200 miles. She attained this point in the above period at an expenditure of 218 tons 6 cwt. coals, averaging 11 tons 13 cwt. per diem. From the 9th to the 13th August, the sea had set strong from the west, the wind moderate from the same direction. The north-east trades were met on the 13th, and retained until the 23rd. During their continuance the average speed was 180 per diem, and consumption of fuel 10 tons 3 cwt. On the evening of the 23rd, the wind veered to south-south-east, and again to south-south-west, with a rough sea setting is from the south-west, which continued for some days.

On the 28th August there remained nearly three thousand miles to perform before reaching Table Bay, Cape of Good Hope, and the quantity of fuel on board 173 tons 14 cwt. It had not been arranged for the Inflexible to coal at any station between England and the Cape, otherwise a direct course might have been kept. This defective arrangement added twelve to fifteen days to the period of her passage, as her commander was now necessitated to diverge from the course, with the view of reaching the south-westerly winds to assist in carrying the Inflexible to the Cape. The equator was crossed on the night of the 29th August, and on the 1st September the Inflexible had disconnected, and was making all sail towards the Brazil coast, with a south easterly breeze, which lasted one week, by which time she reached 21 ° 33 ', her extreme west longitude, in 18 ° 15 ' south latitude. With steam up she met south-westerly breezes, and experienced a rough cross sea on the 9th, which on the 10th changed to a long south-west swell the weather calm ; speed 190, and consumption thirteen tons.

The wind again came from the east, but steam is kept up till the 16th, when being under sail ninety miles only is entered as the day's run. The Inflexible kept under sail, with winds varying from south-east to south-west, until the 26th, when steam was got up, and she made St. Helena Bay, Cape Colony, on the 27th, and was at anchor in Saldanha Bay and Table Bay, on the 28th September, having accomplished the total run from Devonport in forty-nine days, of which thirty-two days was under steam, and seventeen under sail only. From the point of divergence on the 28th of August to the 28th September, the distance run per log was 4363¾ nautical miles, nearly 1500 over the direct course. Her average spend during this period was 140 nautical miles per diem.

Average consumption of fuel per diem, when under steam, 12 tons 6 cwt.

The public service required the Inflexible to remain six weeks at the Cape Colony, and having discharged a portion of her dead weight, and taken on board 460 tons coal, she left Simon's Bay at 2 p.m. of the 8th November, and arrived at Sydney at half-past 8 p.m. on the 13th December, [1846].

The passage from the Cape was performed therefore in 36 days 6½ hours, of which period 160 hours, equal to six days sixteen hours, was under sail only, and the remaining 28 days 14½ hours under steam. During eight days of the passage the practice was to disconnect each morning, and get up steam towards nightfall and on two days and nights the steamer proceeded under canvas. The draught of water in Simon's Bay at starting was fourteen feet six inches forward, and sixteen feet aft - the immersion of paddle wheels five feet six inches. On arrival is Port Jackson she drew thirteen feet; and had about five tons of coal remaining in the boxes. Her average consumption therefore on the passage was 15 tons 17 cwt. daily while under steam.

This passage of the Inflexible is memorable, inasmuch as it is the first steam passage from the Cape to Sydney (from England to the Cape, and thence to India, has been frequently done) ; and it is the longest run at one stretch of any steamer under steam is the annals of steam navigation. I may, therefore, be allowed to deduce more particulars from the copy of the log in my possession.

After leaving the Cape of Good Hope, the course was south-west for a couple of days ; the wind at starting was from south-east ; next day it veered to south-south-west, and a heavy south swell with it : nine flues employed, and plain sail ; consumption, 18 tons 8 cwt. speed, 7½ knots, or eight miles for each ton of coals. The morning of the 11th was variable, but it blew strong from the south-south-west at noon, with a heavy south swell of the sea; speed, 8 1/8th knots. At night the wind came more from the west, and next day it blew a strong gale (the strongest experienced on the passage) from west-north-west ; average speed per log during the day, 8 5/12ths ; but 240 miles were made by observation - the longest run in twenty-four hours, equal to ten knots per hour ; consumption 16½ tons, with double-reef topsails ; ocean swell heavy from the west. On the 13th, the wind was W.S.W., and variable, and a long west swell experienced ; speed per log, about 9 knots, with all plain sail. On the 14th, a north-easterly breeze sprung up, which increased considerably on the 15th, with a rough sea, consumption 14 tons, speed 8¾ per log, - with reef topsails, and 235 N.M. made by observation. On the 16th, it came on again a westerly gale, with a heavy swell, 12 miles per ton consumed of coal, speed 8 1/8th. The 17th moderated, the wind veering from south-east to north-east till the evening of the 18th, when a gentle breeze came on from north-north-west, sea smooth. Steam was let off and studding-sails set. The like on the 19th and 20th, but speed diminishing, steam was got up in the evening. Next day the weather was nearly calm, speed 7 1/9 knots, and 13 1/3 miles per ton of coal; lat. 3° 39' S., long. 68 ° W. On the 22nd there was a moderate breeze from north-north-east, speed 7½. It came again from north-west on 23rd, and steam let off. Next day it was stronger from west-south-west, with a rough sea, proceeded under sail only this and the following day, speed about eight knots. On the 26th November, steam was got up with a south-west wind, and towards evening there was a long west swell, and "ship rolling deeply;" speed 6 3/5, and 12¾ miles to ton of coal consumed. The next day 17 miles were averaged to the ton ; speed 7¾, wind north-north-west. On the 28th, under sail, a long west swell, which continues for some days, steam got up each night. and let off in the morning, until 2nd December. During this period, the wind varied from north-west to south-west, speed about eight knots, with plain sail. There was a heavy swell on the 2nd, and steam was continued from that day continuously to the close of the voyage. On the 3rd, with a gentle south-west breeze, sixteen miles was averaged, for each ton of coal, speed per log, nearly nine knots. On the evening of the 5th, the wind varied, and came light from the north on the 6th, but calm at noon. Latitude 40 ° 23 ' 30 " south. Longitude 131 ° 34 ' east. Nearly sixteen tons of fuel consumed this day.

The next three days the wind was easterly, the consumption increasing, and on the 9th December there was a strong head swell, "heavy from the east," consumption 21 tons 14 cwt., speed 6 5/6 per log, 7 3/5, miles only per ton of coal, being the largest quantity in one day, owing to the head wind and sea, requiring the necessary employment of full steam. On the 10th the weather moderated, the wind still from north-east, consumption. reduced to 17 tons 14 cwt., and speed increased to 7¾ knots. Entering Bass's Straits On the 11th and 12th, having strong north-north-east winds, steering up this coast, speed is rather under 7 knots, consumption on that day 12 tons, 13¼ miles to a ton, which on 12th is reduced to 9 miles per ton ; the consumption having increased to 18 tons. Next evening the Inflexible anchored in Port Jackson.

The speed per log given in the above sketch of the voyage, is the average speed during, twenty four hours. The aggregate of the daily runs on the whole passage, from the Cape to Sydney, is 6400 knots per log, whereas the actual distance is 6600, and allowing for extra latitude being made, the actual ground gone over could not be less than 6700 nautical miles.

The average speed per log, per diem, was 181½ - 7½ per hour:

Taking the actual distance gone over by the Inflexible at 6700 nautical miles; the average speed on the passage was 190 miles per diem, or eight knots per hour, very nearly.

During the passage, the wind came from

The following is a brief summary of the whole voyage from England:

There are circumstances attending the voyage of the Inflexible which detract in some degree from the success, although not from the value of its performance. As a war-steamer, she is not so. well adapted for the purposes of speedy conveyance as some commercial vessels of like capacity, nor does she, in respect to size and power, come up to the Atlantic or Indian packet ships. The nature of the service she had to perform, requiring large stores of ammunition to be conveyed, must have detracted very considerably from her sailing qualities, particularly at the commencement of the voyage ; without question the most remarkable result gained by her voyage is the small quantity of fuel consumed. It must also be recollected that the nature of the passage in respect of winds and weather, under the application of the expansive principle, is of the first importance to this saving in fuel. These satisfactory results therefore may be taken as indicating the favourable nature of the passage to Australia, and the practicability of reducing it to a comparatively limited period, at an expenditure of fuel much less than has ever been imagined. Clearly to perceive the difference, it has to be borne in mind that during this whole passage the full steam was not applied, excepting on leaving port, and on meeting with a heavy sea and head wind ; which occurred very seldom. At all other times the steam acted rather as an auxiliary to the sails, and was lessened or increased according to the force of the wind and the state of the sea. The object was to obtain a tolerable degree of speed at a small consumption of fuel, and the whole voyage was effected at an average of 7 to 8 knots, with as expenditure little more than half what might have been required for the attainment of 9 knots. It may therefore be perfectly practicable to reduce the period of the sea passage to Sydney to 70 days from Plymouth, by the employment of the expansive principle, at a total consumption not exceeding 1000 tons of coal. Superior vessels would probably average 8 knots, by which the sea passage would be 67 days only, reckoning the distance at 13,000 nautical miles. On the other hand, it would require 1800 tons of fuel, and additional coals at two depots, in order to attain a speed of 9 knots, nearly doubling this expense in order to gain five days. There is one part of the voyage which the voyage which the Inflexible does not afford sufficient data, having necessarily made a detour of 1500 miles. It is a matter of some surprise that the Admiralty should have allowed the Inflexible to start on the voyage short of her quantum of fuel, and without the means of obtaining a supply before reaching the Cape of Good Hope. It goes far however to prove the degree of confidence with which steam vessels are now despatched under all circumstances on the most distant voyages

Had the Inflexible made up her quantum at St. Jago, or even Madeira, she might have had 400 tons to steam direct from the Equator to the Cape. The line was reached in twenty days, at an expenditure of 230 tons coal, but there remained only 160 tons to steam a distance of 2800 miles, which through a great portion of the passage might require a daily average consumption of twenty tons. We will suppose that she had been provided, and that her average expenditure was twenty tons to acquire a speed of seven knots. This gives her sixteen days to reach the Cape, at an expenditure of 320 tons, being a saving of 13 days : from which, however, would have to be deducted the time taken in coaling at the depot. On two-thirds of this passage the south-east trades may be expected ; but at certain times of the year they are less strong than others. About the same time of the year the steam-ship Bentinck experienced them very strong ; she steamed from St. Jago in twenty two days. The difficulties of this part of the passage may be considered as adding 100 tons to the consumption for the voyage ; for which reason I have estimated the total consumption for the voyage at 1000 tons. The Inflexible was 153 tons under that amount in steaming 11,000 miles.

The passage made by the Inflexible, from the Cape to Sydney, in all its results, is most satisfactory, and, in certain respects, exceeds the most sanguine expectations. The distance made under steam was not less than 5500 nautical miles, at an expenditure of only 455 tons coals, and a speed of eight knots. The average speed, when under sail only, exceeded seven knots per hour; and there was no occasion in the whole passage, where the steam power could have been increased or applied, to have gained any material advantage.

We will suppose that full steam had been used on the voyage, at an expenditure of 21 tons coals per diem, and estimate the speed at 9½ knots. She would barely have reached King George's Sound, the first harbour, a distance of 5000 N.M., with the 460 tons she had on board, as it would have occupied 22 days very nearly ; two days would have been required at least to take in 200 tons of coal, with which she might have reached Sydney in 8 or 9 days, making the time from the Cape 32 or 33 days instead of 35, at an additional expenditure of 200 tons of fuel, besides the depot expenses. Towards the close of her voyage the Inflexible experienced strong easterly winds and a head sea, which increased her average consumption of fuel to 18 tons for 5 days; in other circumstances her total consumption might have been less by 30 tons.

From the brief summary of the passage from the Cape to Sydney already given, it will be observed that although westerly winds prevailed during twenty days, and were generally strong - sometimes increasing to a gale - steam was not let off. The whole time of her proceeding under sail was two days and part of eight days. Strong south-westerly winds, and a heavy sea from the same direction, are characteristic of this passage above 40 ° south latitude, at which parallel of latitude the Inflexible ran 3000 miles. By keeping up steam during the prevalence of these strong favourable winds, the paddle-wheel steamer saves wear and tear, and steers steadier. The possibility of taking full advantage of these winds by the application of the screw principle, and saving fuel, affords good grounds for supposing that the expenditure of fuel, small as it is by the paddle wheel steamer, will be considerably reduced by the screw application, and without diminishing the speed. The screw principle might also beneficially be applied on the latter part of the passage from England to the Cape as large paddle-boxes catch head winds, and thereby impede the progress of the steam vessel.

Not the least of the many satisfactory results attending the voyage of the Inflexible is the excellent order in which she arrived, and the entire absence of any symptoms of wear and tear. May we not hope that the broad highway of the ocean, which enables the Australian continent to be peopled from Europe, will ere long be lined with a steam marine as efficacious as that for which we are now awaiting the accomplishment by the by-ways of Egypt and the coral reefs of Torres Straits ?

A. Ross.

SG & SGTL ; Vol 4 ; Page 53-4.

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