Chapter XI: TECHNOLOGY.--Impurities in Photographic Chemicals, and (2)

The author said that he hoped to bring before the meeting impartially certain facts which might be of interest, and which, when recorded in the pages of the "Transactions," might be found of some use as data for future reference. In dealing with passenger steamers, he would do so principally from a shipbuilder's point of view; but the moment he commenced to think over Atlantic passenger ships as a shipbuilder, he was met by the question whether the present tendency toward divorcing the passenger and cargo trade from each other is likely to continue or not. If the answer is yes, then it seems to become an important question, for the present at least, how to build, on moderately small dimensions, the fastest, safest, and most economical passenger steamer, using all the most modern improvements to make her commodious and luxurious, and an easy sea boat into the bargain. If cargo is still to be carried in the passenger ships of the future, a moderate speed only will be aimed at in the immediate future, and every effort will be devoted to economy of fuel, comfort, and safety, with a fair carrying capacity. This latter policy is one which may possibly prevail at least for a time, as it has powerful supporters in Liverpool; but he could not help thinking that very high speeds--higher than we have yet attained--must eventually gain the day. He also thought that they were on the eve of important movements, which will indicate what the next step in the passenger trade is to be; for it must be remembered, among other things, that none of our present English transatlantic liners, even the latest, have yet been fitted with the latest modern improvements for economy of fuel or quick combustion, such as triple expansion engines or forced draught. They must, therefore, be at some disadvantage, other things being equal, compared with the ships of the future possessing them. The Great Eastern steaming up Milford Haven about twenty-five years ago between two lines of the channel fleet of old--two and three decked wooden line-of-battle ships--the whole fleet saluting with yards manned, was a sight to be remembered. More than this, that ship, with all her mournful career, has been a useful lesson and a useful warning to all naval architects who seriously study their profession--a lesson of what can be done in the safe construction of huge floating structures, and a warning that the highest flights of constructive genius may prove abortive if not strictly subordinated to the practical conditions and commercial requirements of the times. The Sirius and Great Western crossed the Atlantic in 1838, and in 1840 the first ship of the since celebrated Cunard Company made her first voyage. This was the Britannia, which, with her sister ships, the Arcadia, Caledonia, and Columbia, kept up the mail service regularly at a speed of about 8½ knots an hour. The Britannia was 207 ft. in length between perpendiculars, and 34 ft. 4 in. extreme breadth, 22 ft. 6 in. depth of hold, 423 horse power--nominal--and 1,153 tons burden, built of wood, and propelled by paddles. In 1860 the Collins Line started in opposition to the Cunard, and, after a series of disasters, collapsed in 1858. This was three years after the Persia, the first Cunarder built of iron, had been completed. In 1850, also, the Inman Line was started with the City of Glasgow, of 1,600 tons builders' measurement, and 350 horse power. She was built of iron, and was the first screw steamer sent across the Atlantic from Liverpool with passengers, and was the pioneer of the great emigrant trade which Mr. Inman, above all others, did so much to develop and make cheap and comfortable for the emigrants themselves, as well as profitable to his company. That the builders of the celebrated old Great Britain, in 1843, and Mr. Inman, in 1850, should have pronounced so decisively in favor of the screw propeller in preference to the paddle for ocean steaming is a proof of their true practical judgment, which time and practical experience have made abundantly clear. While the Cunard Company went on developing its fleet from the early wood paddle steamer Britannia of 1,130 tons in 1840 to the iron paddle steamers Persia, etc., in 1858, the iron screw steamer China of 1862, to the still more important screw steamers Bothnia and Scythia, vessels of 4,335 tons, in 1874, the Inman and other lines were as rapidly developing in speed and size, if not in numbers. The year 1874 is memorable, for it saw the White Star steamers Britannic and Germanic put into the water, as well as the Inman steamer City of Berlin and the two before mentioned Cunard steamers, Bothnia and Scythia. By the addition of these two ships to their fleet the White Star Line, although started only in 1870, reached a front rank position in the New York passenger trade. The author gave in separate tables the logs of several of these ships, some from published documents and some kindly furnished by the owners. The Great Western had crossed the Atlantic from Bristol to New York in 15 days as early as 1838. The first Cunard steamer, the Britannic, was about the same speed, from 8¼ to 8½ knots an hour. The average duration of the Cunard voyages in the year 1856 was 12.67 days from Liverpool to New York, and 11.03 days from New York to Liverpool. The Bothnia, in 1874, reduced the passage to about nine days. The White Star Britannic, in 1876, averaged 7 days 18 hours 26 minutes outward from Queenstown to New York, and 9 days 6 hours 44 minutes homeward, and has averaged for the last ten years 8 days 9 hours 36 minutes outward, and 8 days 1 hour 48 minutes homeward. The City of Berlin, of the Inman Line, also built in 1874, 8 days 10 hours 56 minutes, and homeward 8 days 2 hours 37 minutes; and for the nine years from 1875 to 1883 inclusive, averaged outward 8 days 19 hours 56 seconds, and inward 8 days 8 hours 34 seconds; or, putting it into rounder figures, the Britannic had reduced the average passage between the two points to 8¼ days, and the City of Berlin to 8½ days. From the year 1874 on to 1879 no further advance was made in Atlantic steaming, but in that year the Arizona was added to the Guion Line, and it soon became evident that another important stride had been made in the Atlantic passenger trade, which would lead to most important results. The results, as we all know, have been sufficiently startling. The Guion Line, which had started in 1866 with the Manhattan, had now the fastest passenger ship on the Atlantic. In spite of burning some fifty per cent. more coal than the Britannic, the ship was an obvious commercial success. The spirited policy which brought her into existence was appreciated by the public, and the other lines had to move forward. Then followed a period of rivalry, the Cunard Company building the Gallia and Servia, the Inman Company the City of Rome, and the Guion Line the Alaska, all of which were completed in 1881, and afterward the Oregon for the Guion Line--1883--the Aurania the same year for the Cunard Company, and, later still, the America for the National Line, and the Umbria and Etruria for the Cunard Company in 1885.

_Frames from outer edge of Tank to Upper Deck, 7 × 3½ × 8/16 for 250 ft. Amidships, for 60 ft. before and abaft these Points 6½ × 3½ × 6/16 at end of Vessel 5 × 3½ × 7/16, all spaced 24 in. apart and all carried to Upper Deck, double from Bilge to Bilge in way of Engines.--Frames in Tank on Lattice and Solid Floors, 5 × 3½ × 8/16, Intermediate Frames, 8 × 4 × 9/16--Rev: Frames, 4½ × 3½ × 8/16, carried to Upper and Main Deck alternately double, 4½ × 4½ × 8/16 from Bilge to Bilge in E and B space._

Fig. 2--SERVIA.]

Since the completion of the Etruria, for various reasons there has been a pause in the tremendous strides made since 1879, and we may briefly review the results. Taking the Britannic as a standard with her ten years' average of 8¼ days across, and her quickest passage of 7 days 10 hours 53 seconds, we have now the following steamers of higher speeds. Taking them in the order of their absolutely fastest passage out or home, they stand thus:

TABLE I.

---+-------------------------+------+-------+------
| | Days.| Hours.| Mins.
| +------+-------+------
1 | Etruria. | 6 | 5 | 31
2 | Umbria (sister ship). | slightly longer.
3 | Oregon. | 6 | 10 | 35
4 | America. | 6 | 13 | 44
5 | City of Rome. | 6 | 18 | 0
6 | Alaska. | 6 | 18 | 37
7 | Servia. | 6 | 23 | 55
8 | Aurania. | 7 | 1 | 1
---+-------------------------+------+-------+------

It will thus be seen that from the 15 days' passage or thereabout, of the earliest Atlantic steamers, we had got down in the days of the Scotia to about 9 days; in the Britannic to 8¼ days, and, at the present time, we have got to 6¼ days, with seven ships afloat that have done the passage under seven days, and capable of making their average passages range between 6½ and 7¼ days.

Ranged in order of gross tonnage, these eight vessels stand as follows:

TABLE II.

1. City of Rome. 8,144
2. Oregon. 7,375
3. Aurania. 7,269
4. Servia. 7,212
5. Umbria. 7,129
6. Etruria. 7,100
7. Alaska. 6,586
8. America. 5,528

Here the America shows to advantage, for while being eighth in size she is fourth in point of speed, and from what the author can learn, although he had no authenticated details on the subject, he believed she is economical in coal consumption. He might perhaps be permitted to say that one of the most difficult subjects in connection with the propulsion of ships on which to get absolutely accurate data is that of coal consumption. The records of six to eight hours' trials for the purpose of ascertaining the coal consumption are absolutely worthless, as all shipbuilders and engineers know, and so far as English ships are concerned they are never attempted. Foreign owners frequently stipulate for such trials in their contracts with English shipbuilders, and get wonderfully economical results on paper, but the fact that the trials only extend over a few hours renders them valueless, however carefully the coal may be weighed during that period. An authentic record of the absolute quantity of coal consumed, say by each of the eight fastest Atlantic liners, together with their average indicated horse power on the voyage, for a series of voyages, would be extremely valuable.

He gave, in Table III., the consumption per indicated horse power per hour for a number of ships. This table affords valuable data, for it gives, in addition to the dimensions, the moulded draught of water, the midship area, the displacement, the indicated horse power, the speed on trial, the coefficients for the lines both from the block or parallelopipedon, and also from the midship section prism, together with the length and angle of entrance obtained by Kirk's rule, the Admiralty displacement coefficient, together with the coal consumption per day and per indicated horse power per hour.

This table, as will be seen, contains some of the most important of the Atlantic liners, and also a number of other typical ships, which will add a variety to its interest and a value to it. The coefficient, which is contained in the thirteenth column of the table, viz.:

Dis 2/3 × speed³
-------------------------
I.H.P. × sqrt(entrance.)
---------------
10

generally comes out for ships of similar type more nearly a constant in the true sense of the word than the corresponding Admiralty constant. As an example, we have the curves of resistance and horse power for the City of Rome and the Normandie, a large vessel of 6,000 tons, which the Barrow Company built for the Compagnie Generale Transatlantique, in which the coefficient of fineness and the form of the lines pretty closely resemble each other below water; and if we take from the curves the corresponding speeds and horse powers, and work out the constants by the two systems, we have at 14 knots the Admiralty constant for the City of Rome 322.2, and for the Normandie 304.8; and taking for a modified form of constant, the City of Rome gives 253.7 and the Normandie 251.9, which, as will be seen, are much closer together. Similarly, at 15 knots the Admiralty constant for the City of Rome is 310, and for the Normandie 295.2, while a modified constant comes out for the former at 245, and for the latter 244, again agreeing almost identically. The same at 16 knots, for the City of Rome the Admiralty constant comes out 297.6, and for the Normandie 282.8, while a modified constant comes out for the two ships 234.4 and 233.7 respectively, again showing marked agreement. It may be mentioned that in these two ships the engines are of a similar type, being three-crank tandem engines, and the propellers have in both pitch and surface practically the same proportions to the power and speed. The value of these modified constants will probably be found to increase as the speeds increase up to the limit and beyond that point at which wave resistance becomes an important factor.

TABLE III

----------------+--------+---------+---------+-------+-------------+
Name. |Length. | Breadth.| Moulded |Midship|Displacement.|
| | | draught.| area. | |
| | | | | |
| | | | | |
| | | | | |
----------------+--------+---------+---------+-------+-------------+
|ft. in. | ft. in. | ft. in. | | |
| | | | | |
City of Rome | 542 6 | 52 0 | 21 5½ | 1031 | 11,230 |
| | | | | |
| | | | | |
Normandie | 459 4 | 49 11 | 19 9¾ | 892 | 7,975 |
| | | | | |
Furnessia | 445 0 | 44 6 | 22 2½ | 893 | 8,578 |
| | | | | |
| | | | | |
Arizona | 450 0 | 45 1½ | 18 9 | 758 | 6,415 |
| | | | | |
| | | | | |
Orient | 445 0 | 46 0 | 21 4½ | 904 | 7,770 |
| | | | | |
| | | | | |
Stirling Castle | 420 0 | 50 0 | 22 3 | 990 | 7,600 |
| | | | | |
| | | | | |
Elbe | 420 0 | 44 9 | 20 0 | 807 | 6,350 |
| | | | | |
Pembroke Castle | 400 0 | 42 0 | 17 0 | 648 | 5,130 |
| | | | | |
Umbria and | | | | | |
Etruria | 500 0 | 57 0 | 22 6 | 1090 | 9,860 |
| | | | | |
| | | | | |
Aurania | 470 0 | 57 0 | 20 0 | 1020 | 8,800 |
| | | | | |
| | | | | |
America | 441 8 | 51 3 | ----- | --- | 6,500 |
| | | | | |
| | | | | |
Oregon | 501 0 | 54 2 | 23 8 | 1150 | 11,000 |
| | | | | |
| | | | | |
Servia | 515 0 | 52 0 | 23 3½ | 1046 | 10,960 |
| | | | | |
Scotia, P.S. | 369 0 | 47 6 | 19 9 | 867 | 6,000 |
| | | | | |
| | | | | |
Alaska | 500 0 | 50 0 | 21 0 | 949 | 9,210 |
| | | | | |
| | | | | |
Aller | 438 0 | 48 0 | 21 0 | 907 | 7,447 |
| | | | | |
| | | | | |
| | | | | |
Ems | 430 0 | 46 10 | 20 7½ | 877 | 7,030 |
----------------+--------+---------+---------+-------+-------------+

----------------+----------+---------+-----------+-----------+-----------+
Name |Indicated | Speed. | Block | Midship | Prismatic |
| H.P. | |coefficient| section | midship |
| | | |coefficient| section |
| | | | |coefficient|
| | | | | |
| | | | | |
----------------+----------+---------+-----------+-----------+-----------+
| | | | | |
| | | | | |
| | | | | |
City of Rome | 11,890 | 18.235 | .649 | .925 | .702 |
| | | | | |
| | | | | |
Normandie | 6,959 | 16.66 | .614 | .901 | .681 |
| | | | | |
Furnessia | 4,045 | ¹14 | .682 | .903 | .755 |
| | | | | |
| | | | | |
Arizona | 6,300 | 17 | .589 | .895 | .658 |
| | | | | |
| | | | | |
Orient | 5,433 | 15.538 | .621 | .919 | .676 |
| | | | | |
| | | | | |
Stirling Castle | 8,396 | 18.4 | .569 | .889 | .639 |
| | | | | |
| | | | | |
Elbe | 5,665 | 16.571 | .591 | .901 | .655 |
| | | | | |
Pembroke Castle | 2,435.8 | 13.25 | .623 | .623 | .692 |
| | | | | |
Umbria and | | | | | |
Etruria | 14,321 | 20.18 | .538 | .896 | .637 |
| | | | | |
| | | | | |
Aurania | 8,500 | ¹17.5 | .575 | .942 | .632 |
| | | | | |
| | | | | |
America | ----- | ¹17.8 | ---- | ---- | ---- |
| | | | | |
| | | | | |
Oregon | 13,300 | 18.3 | .599 | .849 | .67 |
| | | | | |
| | | | | |
Servia | 10,300 | ¹16.9 | .610 | .862 | .71 |
| | | | | |
Scotia, P.S. | 4,632 | ¹14.31 | .605 | .92 | .65 |
| | | | | |
| | | | | |
Alaska | ----- | ---- | .614 | .904 | .679 |
| | | | | |
| | | | | |
Aller | 7,974 | 17.9 | .590 | .899 | .656 |
| | | | | |
| | | | | |
| | | | | |
Ems | 7,251 | 17.55 | .593 | .907 | .652 |
----------------+----------+---------+-----------+-----------+-----------+

----------------+------------+-----------------+-----------------+
Name. | D 2/3 × S³ | D 2/3 × S³ | Kirk's system. |
| ---------- | --------------- | |
| I.H.P. | _____ +---------+-------+
| |I.H.P. × \/ent. |Length of|Angle. |
| | ------- |entrance.| |
| | 10 | | |
----------------+------------+-----------------+---------+-------+
| | | | |
| | | | |
City of Rome | 255 | 201.3 | 161.27 | 8° 29'|
| | | | |
| | | | |
Normandie | 265 | 219.5 | 146.41 | 8° 44'|
| | | | |
Furnessia | 284 | 273 | 108.7 |10° 28'|
| | | | |
| | | | |
Arizona | 269.2 | 217 | 153.79 | 7° 30'|
| | | | |
| | | | |
Orient | 270.8 | 225 | 144.17 | 8° 21'|
| | | | |
| | | | |
Stirling Castle | 286.8 | 233.7 | 151.3 | 8° 22'|
| | | | |
| | | | |
Elbe | 275.5 | 229 | 144.6 | 7° 56'|
| | | | |
Pembroke Castle | 284 | 258 | 122.9 | 8° 49'|
| | | | |
Umbria and | | | | |
Etruria | 260 | 191.8 | 184 | 6° 52'|
| | | | |
| | | | |
Aurania | 266 | 204.6 | 170 | 8° 38'|
| | | | |
| | | | |
America | --- | --- | --- | ----- |
| | | | |
| | | | |
Oregon | 227.9 | 190 | 164.3 | 9° 39'|
| | | | |
| | | | |
Servia | 231 | 192 | 145.3 |10° 42'|
| | | | |
Scotia, P.S. | 208.9 | 186 | 126.8 |13° 21'|
| | | | |
| | | | |
Alaska | --- | --- | 160.23 | 8° 2'|
| | | | |
| | | | |
Aller | 277 | 225 | 150.6 | 8° 10'|
| | | | |
| | | | |
| | | | |
Ems | 273 | 223 | 149.4 | 8° 40'|
----------------+------------+-----------------+---------+-------+

----------------+------------+--------------------+----------------+--------+
Name. | Coal | Cylinders | Boilers | Working|
|consumption | | |Pressure|
|-----+------+-------------+------+--------+-------+ |
| Per | Per | Diameter |Stroke|Heating | Bar | |
| day |I.H.P.| | |surface |surface| |
| | | | | | | |
----------------+-----+------+-------------+------+--------+-------+--------+
| | | Ins. | Ins. | | | lbs. |
| | |/3 @ 46 \| | | | |
City of Rome | 185 | 2.2 |\3 @ 86 /| 72 | 29,286 | 1398 | 90 |
| | | | | | | |
| | |/3 @ 35-7/16\| | | | |
Normandie | 148 | 2 |\3 @ 74-7/8 /| 67 | 21,404 | 756 | 85.2 |
| | | | | | | |
Furnessia | 97 | 2.2 | 49-100 | 66 | 10,396 | 440 | 90 |
| | | | | | | |
| | |/1 @ 62 \| | | | |
Arizona | --- | --- |\2 @ 90 /| 66 | ---- | ---- | 90 |
| | | | | | | |
| | |/1 @ 60 \| | | | |
Orient | --- | --- |\2 @ 85 /| 60 | ---- | ---- | 75 |
| | | | | | | |
| | |/1 @ 62 \| | | | |
Stirling Castle | --- | --- |\2 @ 90 /| 66 | 21,161 | 787 | 100 |
| | | | | | | |
| | |/1 @ 60 \| | | | |
Elbe | --- | --- |\2 @ 85 /| 60 | ---- | ---- | --- |
| | | | | | | |
Pembroke Castle | 44 | 1.7 | 43 and 86 | 57 | 7,896 | 288 | 99 |
| | | | | | | |
Umbria and | | |/1 @ 71 \| | | | |
Etruria | 315 | 2.1 |\2 @ 105 /| 72 | 38,817 | 1606 | 110 |
| | | | | | | |
| | |/1 @ 68 \| | | | |
Aurania | 215 | 2.2 |\2 @ 91 /| 72 | 23,284 | 1001 | --- |
| | | | | | | |
| | |/1 @ 63 \| | | | |
America | 185 | --- |\2 @ 91 /| 66 | ---- | 882 | --- |
| | | | | | | |
| | |/1 @ 70 \| | | | |
Oregon | 310 | 2.2 |\2 @ 104 /| 72 | 38,047 | 1428 | 110 |
| | | | | | | |
| | |/1 @ 72 \| | | | |
Servia | 205 | 2 |\2 @ 100 /| 78 | 27,483 | 1014 | --- |
| | | | | | | |
Scotia, P.S. | 168 | 3.4 | | -- | ---- | ---- | --- |
| | | | | | | |
| | |/1 @ 68 \| | | | |
Alaska | --- | --- |\2 @ 100 /| 72 | ---- | ---- | 100 |
| | | | | | | |
| | |/1 @ 44 \| | | | |
Aller | --- | --- ||1 @ 70 || 72 | 22,630 | 799 | 150 |
| | |\1 @ 100 /| | | | |
| | | | | | | |
| | |/1 @ 62 \| | | | |
Ems | --- | --- |\2 @ 86 /| 60 | 19,700 | 780 | 100 |
----------------+-----+------+-------------+------+--------+-------+--------+

¹Mean speed of a voyage across the Atlantic Ocean.

The author next considered the strains to which a ship is exposed, and stated that he had before him the calculations for three of the largest vessels, two of them of iron and the other of steel; and he found, in the case of the iron, the maximum tension on the gunwale during the greatest hogging strains likely to be endured at sea would not exceed about six tons per square inch, while in the case of the steel ship it is only about 6½ tons. These strains are well within the limits of safety, and a comparison of the scantlings of these with the others justifies the assertion as to their general safety from a structural point of view. The sections of these three ships are shown in Figs. 1, 2, and 3, with their principal scantlings. It will be seen from these sections that the three ships differ materially in their mode of construction. In the case of Fig. 1, which represents the City of Rome, the largest of the three, it will be seen that the main framing of the vessel is entirely transverse, with very heavy keelsons in the bottom, and large partial bulkheads or web frames, and the outside plating arranged on what is termed the edge to edge principle, with a great portion of it double. In the next section, Fig. 2, the Servia, which is built of steel, on the other hand, the bottom is built on the longitudinal cellular system, the first application, he believed, of this system to an Atlantic liner. The plating of the Servia is of the usual alternate outer and inner strake system, partly double; while the third section, the Oregon, approaches more nearly to the ordinary system of framing and plating usually adopted, but it will be seen that she was well tied in the bottom by very heavy intercostal and plate keelsons, as well as in the top by heavy stringers and sheer strakes, with much of her plating doubled, and heavy web frames inside. The author next considered the question of stability, and went on to deal with the subject of twin screws, and stated that the Barrow Shipbuilding Company has done more in the way of planning and designing for the adoption of twin screws lately than for any other mode of propulsion, and this chiefly for passenger steamers. He did not attach much importance to the particular form of the blade either in single or twin screws, as he believed so long as the disk area, the surface, and pitch were properly adjusted to the speed of the vessel, and to enable the engines to use, at the maximum speed, just the full quantity of steam that the boilers can make, we have got pretty nearly as far as we can get. To fix these dimensions of the propeller accurately at the present time, and without further knowledge of the action of the screw on the water, was, he thought, impossible. All the rules and formulæ are empirical. The best one he knew is given in Table IV., due to Mr. Thom, the head of the Barrow Company's engineering drawing office, and at present acting manager, who has used it for some years in practice. These formulæ are based upon the assumption that the area of propeller disk should be proportional to the indicated horse power, divided by the cube of the speed, and the same with the projected area of the propeller and also the surface.

TABLE IV.

_Particulars of Propellers and Constants._

------------------------------+-------+---------+----------+-------------- | Length| | Proj. | Feet per Ship. | of | Disk | surf. | minute. | ship. |constant.| constant.|Speed of tips. ------------------------------+-------+---------+----------+-------------- City of Rome. | 542 | 220 | 69 | 4,715 Normandie | 459 | 250 | 66 | 4,099 Furnessia | 445 | 223 | 69 | 3,654 Eden | 300 | 211 | 64 | 3,080 Yorouba | 270 | 213 | 63 | 3,202 Taygete | 260 | 238 | 56 | 3,166 Kow-shing | 250 | 171 | 69 | 3,369 S.Y. Monarch | 152 | 221 | 65 | 4,040 S.Y. Aries | 138 | 179 | 56 | 2,986 Twin screw Fenella | 200 | 244 | 64 | 2,890 Twin screw H.M.S. Fearless[2] | 220 | 277 | 67 | 5,022 Twin screw H.M.S. Iris | --- | 454[6]| 135[6] | --- Twin screw H.M.S. Iris [3] | 300 | 412 | 221 | --- Twin screw H.M.S. Iris [4] | 300 | 346 | 99 | 4,961 Twin screw H.M.S. Iris [5] | 300 | 439 | 82 | 5,309 ------------------------------+-------+---------+----------+-------------

[Footnote 2: Estimated with a speed of 17.5 knots and 3,370
I.H.P.]

[Footnote 3: With the first propeller at the estimated speed of
17.5 knots and 7,000 I.H.P.]

[Footnote 4: With four bladed modified Griffith's on actual
trial.]

[Footnote 5: With two bladed modified Griffith's on actual trial.]

[Footnote 6: Constants obtained from first propeller calculated
from a speed of 18.5 knots and 7,500 I.H.P.

Area of propeller disk × speed of ship in knots.³
Disk constant = --------------------------------------------------
I.H.P.

Projected Projected area of propeller × speed of ships in knots.³
area = ------------------------------------------------------
of constants I.H.P.

Expanded area constants may be obtained and used in the same way.]

The discussion which followed was opened by Mr. Holt. He said that if they were to have greater speed on the Atlantic, there was one point which was not alluded to in the paper, and that was the total abolition of cargo on board the great passenger steamers. If vessels were built solely for passenger traffic, they would be able to insure greater speed by reason of the greater slightness in build and the additional space at the command of the designer. The existing Atlantic express steamer was far too heavy, and might, if cargo was dispensed with, be made with finer lines and more yacht-like. He looked on the proposition to fit such vessels with longitudinal bulkheads with great fear. If a collision took place--such, for example, as that which sunk the Oregon--water would get access to one side only of the ship, and it was not at all improbable that if a sea was on, she would turn right over. At all events, very serious risk would be involved.

Mr. W.H. White, Chief Constructor to the Admiralty, said the question of twin screw propulsion was one of special interest to himself, and had been so for many years. In 1878 he dealt with it as fully as he then could on the basis of the Admiralty data, and he then ventured to say everything in favor of twin screws that Mr. John had said in his paper. If greater power than that now used in such a ship as the Etruria, for example, were demanded, two screws must be used. Good as are the results obtained with the Etruria, it was by no means certain that still better might not be had. If she had been fitted with two screws instead of one, very great advantage would be gained by the greater submergence of the twin screws, as thus racing would be almost wholly prevented.

Mr. Calvert urged that more attention should be devoted to studying the relative values of different portions of the propeller.

The sitting was then suspended. In the afternoon, as we have already stated, the members visited the steamship Germanic on the invitation of Messrs. Ismay, Imrie & Co., subsequently proceeding to Messrs. Cope Brothers' tobacco works, and thence to the exhibition, where the dinner of the Institution took place in the evening.

On Friday morning no paper was read; some official business was transacted, and this being done, the discussion on Mr. John's paper was resumed.

Mr. Biles remarked that there were many advantages in the use of twin screws which had not been sufficiently taken into account. When a ship with twin screws was being handled in dock there was greater maneuvering power, and therefore less liability for the ship to come in contact with the walls, although, if she did so, there would be greater probability of damage to the propellers. He thought means could be easily devised of protecting the screws when the ship was in dock. Another of the incidental advantages connected with twin screws was that smaller engines and smaller propellers were required, and therefore they might run them at a higher speed. They would also get lighter machinery with twin screws, and there would be less liability to have bad castings and forgings in the smaller engines, and of course the cost would be less.

With respect to the question of the middle line bulkheads, he could not quite agree with Mr. John as to the great advantages of them in a big passenger steamer. He thought there would be greater difficulty in managing a ship so built if she was in danger of sinking. Increased subdivision in a longitudinal direction was a very desirable thing, and almost necessary for a condition of immunity from sinking. In future Atlantic steamers longitudinal bulkheads should be placed not in the middle line, but nearer the sides of the ships, and they should recognize the fact that they had engines and boilers in different compartments, and make arrangements whereby the ship would still float, although the doors in these compartments were kept open. The proper way to arrive at that was to have a ship with great beam, and to have two longitudinal bulkheads at considerable distances from the sides of the ship, subdivided as completely as possible, both under and above water, so that, even supposing they got water into the space between one bulkhead and the side of the ship, they would have sufficient buoyancy in the other parts of the ship to keep her afloat. Broad ships must necessarily mean deep ships, in order to have comfort at sea. They were limited in length, and first came the question how many passengers they wanted to carry. The experience of a ship like the America--which was only 400 ft. in length--showed it was not necessary to go to great length to have great speed. A ship of 400 ft. to 430 ft. in length, 65 ft. of beam, and with a depth of 45 ft., would be a ship of proper dimensions for the Atlantic trade, and he believed it quite possible to build a vessel of special construction of about 7,000 tons gross register which should steam with less consumption of coal than the Umbria and Etruria at a rate of 22 knots, crossing the Atlantic from Liverpool to New York in six days. He thought that was likely to be the vessel of the future, and that it would be quite as commercially successful as the Umbria or Etruria.

Mr. J. Campbell remarked that at present the great American liners had only the ordinary compound engines, and he thought that, instead of converting them to triple expansion, they should take a step further at once, and adopt quadruple expansion engines. This class of engines was being very successfully built in various parts of the country. He should recommend the adoption of a three-crank six-cylinder engine.

Mr. Hamilton did not think it had been demonstrated that greater efficiency had been got out of twin screws than out of single screws; but there was no doubt they would tend to additional safety.

Mr. Martell said that when they had got satisfactory data, twin screws would be adopted for ships requiring great speed; but they had not got that data at present.

Admiral Sir John Hay, referring to twin screws as applying to sea-going steamers which might be employed for imperial defense, said it was quite certain that the defense of their extended commerce would always require to be assisted by ships such as the Oregon and other magnificent vessels which had been used for that purpose on a recent occasion. He believed that for war purposes the twin screw was recognized by all naval men as having very many advantages. If that were so, it was quite evident that it would be a great advantage, under such conditions as occurred at the loss of the Oregon, if the compartments could be made completely water-tight; and the twin screw, with the separation of the ship longitudinally, gave them the very greatest possible protection. They could not trust to bulkheads that were only closed occasionally by doors. What was required for war purposes was the entire and complete isolation of different parts of the ship, having always practically closed communications between them.

Mr. John then replied on the general discussion. He was pleased to find that they had faith in the future of the twin screw and of subdivision. The public had a right to demand greater safety than they at present had on the Atlantic, or could have with a single screw.

* * * * *

EXAMINATION QUESTIONS IN GENERAL CONSTRUCTION.

The following is a copy of the last examination paper given to candidates who are desirous of employment in the constructive departments of the municipality of New York:

N.B.--In case candidate does not remember formula or method of solving any problem submitted to him, let him name any work upon the subject where such formula or method may be found.

1. What is civil engineering?

2. Have you ever pursued a course of study in any educational institution, or with any civil engineer, which would fit you for the position of assistant engineer? If so, state when and with whom; state also, in detail, what experience you have had.

3. Have you ever had responsible charge of any public work? If so, state particulars.

4. Solve the following according to the algebraic signs:

--------------------------------------
/ (6-2/7 - 4-3/9) × 8-7/16
/ ------------------------ × 67873.367, and show your work.
\/ 4-4/12

5. The population of a certain town in 1880 was 7,095; it having increased 25 per cent. in ten years, what was it in 1870? Show your work.

6. How many feet, board measure, in the flooring of a room 20 feet by 30 feet and 2½ inches thick?

7. Find value of x and y in the following equations:

2 x + 3 y = 33
4 x - y = 17.

8. Find value of x in equation x² - x - 40 = 170.

9. Find value of x in equation

--------
a / a² - x² x
- + / ------- = -
b \/ x² b

10. Explain the meaning of the expression a½ × b¾.

11. What is a logarithm?

12. What is the base of the common system?

13. In making what calculations are logarithms useful?

14. How do you find the logarithm of a number in a table of logarithms?

15. What are similar triangles?

16. How are similar triangles proportioned to each other?

17. The sides of a polygon being prolonged, what is the sum of all the exterior angles equal to?

18. How do you pass the circumference of a circle through three given points not in the same straight line?

19. How do you describe a square in a circle?

20. In the triangle, b being a right angle, what proportion does d b bear to a d and d c?

21. How do you inscribe a regular hexagon in a circle?

22. What proportion do circumference and areas of circles bear to their radii?

23. How do you find the area of a regular polygon?

24. Of an irregular polygon?

25. Of a circle?

26. How do you find the solid contents of a cylinder?

27. Of a wedge?

28. Of a pyramid?

29. Find the contents of the wedge, base 20 feet by 30 feet, height 10 feet, edge 15 feet.

30. State the prismoidal formula; would you use it in calculating earthwork?

31. Is a simple question in calculating areas.--Ed. _Eng. News_.

32. How many and what parts of a plane triangle must be given to find the rest?

33. Define the terms sine, co-sine, tangent, and co-tangent.

34. What are natural sines, co-sines, etc.?

35. What is a table of logarithmic sines, co-sines, etc.?

30. Two sides and two angles of a plane triangle being given, how do you find the other parts?

37. When two sides of a plane triangle and their included angles are given, how do you find the other parts?

38. In the right-angled triangle, A B H express algebraically the value of the sine, co-sine, tangent, and co-tangent of angle A in terms of a, b, and h, they being the altitude, base, and hypothenuse of the triangle.

39. What is the law of gravitation?

40. Do you understand that there is any difference in the meaning of the terms gravitation and gravity?

41. What is the law of falling bodies?

42. Express algebraically this law, taking v = velocity of falling body; g = acceleration of gravity; and h = height.

43. What is the center of gravity of a body?

44. How is it found?

45. Where is the center of gravity of a homogeneous body whose sides are all rectangles?

46. What is the specific gravity of a body?

47. What is the standard for solids and liquids?

48. What for gases?

49. What laws govern the pressure of liquids at rest?

50. How do you find the number of gallons of water to the cubic foot?

51. What is the weight of a gallon of water?

52. What is the pressure per square inch on the side of a vessel at the depth of 10 feet below the surface of the water?

53. What will be the theoretical volume of discharge per second from a reservoir through a pipe 1 foot in diameter, discharging at a depth of 100 feet below the surface of the water?

54. How many gallons of water will be discharged through a pipe 1 foot in diameter, 328 feet long, head 13½ feet, coefficient of flow = 0.007?

55. State how many men are needed to make up a full party for a survey of a preliminary line or location of a public work, such as a railroad or aqueduct.

56. State also their several duties.

57. For what purpose is the magnetic needle used in surveying land?

58. What is a traverse table and for what used?

59. How do you set out a circular curved line upon the ground?

60. If an obstacle occurs to alignment, state how you would overcome it upon straight lines, also upon curves.

61. The radius of a curve being given, and angle of intersection of the two tangents, how do you find the length of the tangent from their intersection to the beginning of the curve?

62. Describe an engineer's transit, and name its adjustments.

63. Describe a Y level, and name its adjustments.

64. How many kinds of leveling rods do you know of?

65. State how they are graduated, and how they can be read to the 1/1000 of a foot.

66. Show a form of field-book for transit notes used when "running" curves, and place thereon notes of a 5 deg. curve for 1,000, with two intermediate "set-ups."

67. Show a form of level-book, and place therein sufficient figures to show your method.

68. What are cross-sections?

69. How do you set slope stakes for excavation and embankment?

70. What is a grade line?

71. What proportion of the breaking weight of a beam would you consider a safe load?

72. With the load uniformly distributed, what fractional part of the whole weight may be considered, in all calculations, as being carried at the center?

73. Suppose a beam supported at both ends, and take w = weight, l = length of beam, b = breadth, d = depth, s = breaking weight. Express algebraically the value of s in terms of the other quantities.

74. Sectional area being 36 square inches, which would be the stronger section, 6 by 6 or 4 by 9?

75. Make a design for a pair of rafters, connected by a tie-beam, for a roof 30 feet span, showing the dimensions of the several parts and the manner of connecting them. State in detail your method of obtaining the several dimensions.

76. How do you apply the principle of the parallelogram of forces in determining the strain on the various members of a structure? Illustrate graphically.

77. What should be the thickness at the top and base of a retaining wall 15 feet high, built to retain ordinary earth? Show your method of obtaining the required dimensions, also a sketch of the wall, showing how it should be founded.

78. A reservoir is to be built, depth of water 10 feet. If the walls are built of masonry, find the thickness of the same, and state how they should be built. Show your work.

79. What is an arch, of how many forms, and of what may it be constructed?

80. Can you state how you would find the thickness of an arch of stone, span and rise being given?

81. Define the intrados and extrados of an arch.

82. Where should the line of resistance to pressure be found in an arch in order to retain its stability?

83. Can you find the thickness of the abutments, the rise and span of the arch being given?

84. In a semicircular arch, where is the horizontal thrust greatest and where least?

85. Name the common kinds of stone used in building.

86. Define the terms "quarry-faced," "rough-pointed," "fine-axed," "bush-hammered," as applied to the dressing of stone.

87. Describe "rubble" masonry, "ashlar" masonry, and "broken ashlar" masonry.

88. What are "headers" and "stretchers"?

89. What should be the proportion of "headers" to "stretchers"?

90. How would you prepare the foundation for a heavy wall, and how deep should it be excavated?

91. How are walls founded on soft or yielding materials?

92. Describe a good quality of bricks, and state how you would know a good brick from a poor one.

93. In how many ways is brickwork "bonded" to make good work in heavy walls?

94. What is hydraulic cement, and how many kinds do you know of?

95. Which do you consider the better quality, Rosendale or Portland, and why?

96. What is mortar composed of, and how mixed?

97. What kind of sand should be used, and how do you test its quality?

98. What is the meaning of the term "setting" as applied to cement?

99. How would you test cement?

100. What is concrete, of what composed, and in what proportion should its ingredients be mixed?

101. Name the common kinds of wood used in building.

102. What kind of timber resists decay longest under ground?

103. How may timber be preserved from decay?

104. What do you understand by limit of elasticity as applied to a beam under strain or pressure? What is meant by the neutral axis of a beam?

105. What is the tensile strength of a good quality of wrought iron per square inch?

106. For what parts of a structure may cast and wrought iron be used in reference to tension and compression?

107. Make a sketch of the form of cast-iron beam best adapted to resist a transverse strain.

* * * * *

CELEBRATION OF THE FIVE HUNDREDTH ANNIVERSARY OF THE UNIVERSITY OF HEIDELBERG, AUGUST, 1886.

The wave of pleasure and enjoyment which flooded everything has passed. Heidelberg, usually so quiet, assumed the role of a city of the world, and all was bustle and excitement in the streets, which were hung with flags and other decorations. The trains constantly brought new accessions to the crowd, and gayety and mirth reigned supreme.

The dedication of the renovated _Aula_ of the University served as a prelude to the festivities of the week. On this occasion a splendid flag, embroidered by order of the wives of the faculty of the Academy, an equally costly cover for the scepter, and a silver inkstand were added to the treasures of the University. Conspicuous among the numerous presents received were a richly carved set of furniture--the gift of former students from Switzerland--and all the publications of certain book dealers.

On the afternoon of August 2, the Grand Duke and Duchess arrived in Heidelberg, where they were received with much enthusiasm. They remained at the modest palace during the time of the jubilee, and whenever they appeared they were greeted with expressions of patriotism and love. On the evening of the 2d, the _Oberburgermeister_, Dr. Wilckens, extended a hearty welcome to the guests who had gathered in the over crowded hall. Vincenz Lachner conducted the musical part of the entertainment, which was charming. The German Crown Prince arrived early on the 3d, so as to accompany his royal cousins to the service in the beautifully decorated _Heiliggeistkirche_, on which occasion Prof. Bassermann spoke with great effect. At 11 o'clock, the Court appeared in the _Aula_, where the Grand Duke presided, in virtue of his office of "Rector Magnificentissimus." His address was followed by those of the Crown Prince; the _Prorector Geheimrath_, Dr. Bekker; Edward Zeller, of Berlin; Jules Zeller, of Paris; and others. In the evening the citizens and strangers were attracted to the _Jettenbühel_ by the festival at the castle; from 7:30 until 10 o'clock the nobility held court in the _Bandhause_. The scene was like fairyland, all the outlines of the castle were marked by thousands of small lights, and the court was lighted by great candelabra. In the ever-increasing crowd it was difficult to find a place and to obtain refreshments, which were given out in immense quantities by the State.

On the morning of the 4th the people thronged again to the _Heiliggeistkirche_ to listen to the address of the _Geheimrath_, Dr. Kuno Fischer, on the fate of the Palatinate and Heidelberg, which was preceded and followed by music. After this the participants in the festival were brought together by a dinner in the Museum Hall, and seldom have speeches so inspired an audience as did those of the Grand Duke and the Crown Prince. Never has Heidelberg seen such a torch-light procession as that formed by the students in honor of their Rector; 3,000 torches lighted him to the City Hall. He thanked them, and proposed cheers for the Crown Prince.

On the morning of the 5th there was the presentation of degrees. In the afternoon a special train carried four hundred people to Karlsruhe, where the royal party held a great reception. The capital was decorated with flags, the city parks were lighted with Bengal lights, there was music, and a song by the patriotic bard Vierordt was sung.

All the splendor and interest shrank into insignificance before the grand historical procession on the morning of the 6th, which made a lasting impression on the minds of all. The throng of 100,000 people watched quietly while the whole history of the Palatinate passed in review before them. The procession illustrated this history much better than it could have been told by any professor or any book. There was not a vacant space to be found, extra trains having brought more spectators, and yet everything passed off quietly and without accident. In the evening there was a heavy shower, which freshened everything, leaving no ill effects to be seen the next morning, which was more than could be said of many of those who attended the imposing _Commerse_ of the Heidelberg students. As a former student, the Grand Duke appeared among the 6,000 visitors at the _Commerse_, where he presided and spoke enthusiastically of the Emperor. Other speeches followed, until the conversation became so animated that even Von Treitschke, who was received with an ovation, could not be heard. At midnight the court retired and the _Fidelitas_ succeeded to their rights.