1830.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



301 



independency and specinlity. It was in our return voyage from 

 America that the highest seas occurred, when the circumstances 

 adapted for interesting ohservations were singularly favourahle; 

 fur, whilst the magnitude and the peculiar construction of the 

 upper works of the ship — the HibernUi — afforded various platforms 

 of determinate elevation above the line of flotation for ohserva- 

 tions on the height of the waves, the direction of tlie ship's course, 

 with respect to that of waves, was generally so nearly similar as to 

 yield the most advantageous agreement or accordance for ohserva- 

 tions on their width and velocity. These observations I shall ex- 

 tract, in their order, from my journal kept during the homeward 

 passage. 



My first observation worth recording is under the date of 

 March 5, 184-9, when the ship was in latitude about 51°, and longi- 

 tude (at noon) 38' 50' W. — the wind then being about W.S.\V'., 

 and tlie shiji's course, true, X. 52° E. At sunset of the itli the 

 ■w'lml h\ew a. Iiiird gnle, which, with heavy sipialls, had continued 

 during the night; so that all sail was taken in but storm-staysail 

 forward. The barometer stood at '29-50 at 8 p.m., but fell 

 so rapidly as to be at 28-30 by 10 the next morning. In the 

 afternoon of this day I stood some time on the saloon deck or 

 cuddy roof — a height, with the addition of that of the eye, of 

 23 feet 3 inches above the line of flotation of the ship, — watch- 

 ing the sublime spectacle presented by tlu» turbulent wati^rs. I 

 am not aware that I ever saw the sea more terribly magnificent. 

 I was anxious to ascertain the height of tliese iniglity waves; but 

 found almost every wave rising so nuich above the level of tlie eye, 

 as indicated by the intercejiting of the horizon of the sea in the 

 direction in which they approached us, as to yield only tlie mini- 

 mum elevation, and to show that the great majority of these rolling 

 masses of water possessed a height of considerably more than 21- 

 feet (including depression as well as altitude), or, reckoning from 

 the mean level of the sea, of mure than 12 feet. Exposed as the 

 situation was, I then adventured to the larboard paddle-box, which 

 was about 7 feet higher, where tlie level (as ascertained afterwards 

 at Liverpool, allowance being made for the alteration in the 

 draught of water of the ship,) was 2-1 feet 9 inclies above the sea. 

 This position, witii 5 feet (i inches, the height of my eye, gave an 

 elevation altogether of 30 feet 3 inches for the level of the view 

 then obtained, — a level, it should be remarked, which was very 

 satisfactorily maintained during the instants of observation, be- 

 cause of the whole of the ship's length being occujiied witiiiii the 

 clear '• trnnijh of the sea," and in an even and upright position, 

 whilst the nearest approaching wave had its ma.ximum altitude. 

 Here, also, 1 found at least one-hn(fof tlie waves which overtook 

 and passed the ship were far above the level of my eye. Fre- 

 quently I observed long ranijes (not acuminated peaks) extending 

 lUO yards, perhaps, on one or both sides of the ship, — the sea then 

 coming nearly right aft, — which rose so high above the visible 

 horizon, as to form an angle estimated at 2 to 3 degrees (say 2.L°) 

 when the distance of the wave summit was about 100 yards fi-om 

 the observer. This would add near 13 feet to the level of the eye. 

 And this measure of elevation was by no means uncommon, — 

 occurring, I should think, at least once in half-a-dozen waves. 

 Sometimes peaks of crossing or crests of breaking seas would shoot 

 upward at least 10 or 15 feet higher. The aeerage wave was, I 

 believe, fully equal to that of my sight on the paddle-box, or more, 

 that is, '■'^ := 15 feet, or upwards; and the mean highest vmves, not 

 including the broken crests, about 4-3 feet above the level of the 

 liollow occupied at the moment by the ship. Illuminated as the 

 general expanse not unfrequently was by the transient sunbeam 

 breaking through the heavy masses of the storm-cloud, and con- 

 trasting its silvery light with the prevalent gloom, yielding a wild 

 and partial glare, the mighty hills of waters rolling and foaming 

 as they pursued us, whilst tiie gallant and buoyant ship — a charm- 

 ing "sea-boat" — rose abaft as by intelligent anticipation of their 

 attack, as she scudded along, so tliat their irresistible strength and 

 fierce momentum were harmlessly spent beneath her and on her 

 outward sides, — the storm, falling fiercely on the scanty and 

 almost denuded spars and steam chimney raised aloft, still indi- 

 cated its vast, but as to us innoxious, power, in deafening roarings, 

 altogether presented as grand a storm-scene as I ever witnessed, 

 and a magnificent example of " the works of the Lord," specially 

 exhibited to sea-going men, "and his wonders in the deep." In 

 the afternoon of the same day the gale again increased, blowing, 

 especially during the continuance of a much protracted hail- 

 shower, terrifically, — roaring like thunder whilst we scudded be- 

 fore it, causing the ship to vibrate as by a sympathetic tremor, and 

 the tops of rolling waves, too tardy, rapid as was their actual 

 progress, for the speed of the ass;aling influence, to be carried off 



and borne along on the aerial wings in a perfect drift of spray ! 

 But during the jieriod of these most vehement operations of nature, 

 1 was fortunately enabled, from familiarity with sea enterprise, to 

 pursue my observations with entire satisfaction. 



The next day— March (j— added to the interest of these investi- 

 gations by developing the character of the Atlantic waves under a 

 long and fiercely-continued influence of a little varying wind. It 

 had blown a heavy gale, violent in the showers, fnmi the north- 

 westward, from Saturday evening the 4th, to the evening of Sun- 

 day, from 26 to 30 hours; during the night, too, of Sunday, it had 

 again blown hard (abating towards the morning of Monday), and 

 making a total continuance of the storm, in its violence, of about 

 36 houi-s.* I renewed my observations on the waves at 10 a.m. — 

 the storm having been then subdued for several hours, and the 

 height of the waves having perceptibly subsided. Soon I observed, 

 when standing on the saloon-deck, that ten waves, in one case, 

 came in succession, which ;ill rose above the apparent horizon, — 

 consequently they must have been more than 23 feet, probably the 

 average might be about 26 from ridge to hollow. At this period I 

 also found that occasionally (that is, once in about four or five 

 minutes), three or four waves in succession, as seen from the )iad- 

 dle-box, rose aboi'e the visible horizon — hence they i.uist, like tliose 

 of the preceding day, have been 30 feet waves. But one important 

 difference should be noted — viz., that they were of no great extent 

 on the ridge, presenting, though more than mere conical peaks, 

 but a moderate elongation. Another subject of consideration and 

 investigation, on this occasion, was the period of the regular 

 waves overtaking the shij), and the determination, proximately, of 

 the actual width or intervals, and their velocity. — I. The ship was 

 then going nine knots only, the free action of the engines being 

 greatly interfered with by the heavy sea running, and the lines of 

 direction of the waves and the ship's course dift'ered about 22.^ 

 degrees, the sea being two points on the larboard quarter— in 

 other words, the true course of the ship was east; the direction 

 from whence the sea came was W.N.W. 



2. The period of regular waves, in incidental series, overtaking 

 the ship were observed as follows: — 



Waves. Min. Spo. 

 •2 ' occupied .'» 30 

 10 „ 2 :i5 

 10 „ a :m 

 10 „ a 45 



9 „ 3 IS 



Mean. 



16.5" 



15-;." 



IT-U" 



160" 



17 t" 



General average ltJ-5" 



3. The length of the ship was stated to be 220 feet. The time 

 taken by a regular wave to pass from stern to stem appeared, on 

 a mean of several observations, to be about six seconds, llence 

 6 ' : 220 feet (the width passed over in that time) : : 16-5 feet to 

 605 feet (the width passed o\er betwixt crest and crest.) But 

 this extent, by reason of the obliquity of the direction of the 

 w aves to the course of the ship, is found to be elongated about 45 

 feet, reducing the probable mean distance of the waves to 551ii feet. 

 Independently of this process, I had previously estimated the dis- 

 tance of the wave crests, ahead and astern when the ship was in 

 the hollow, as 1 stood near the centre of the ship's length on the 

 paddle-box, at 300 feet each way, by comparing the intervals be- 

 twixt my position and the place of the wave-crest, with the known 

 length of the ship. This comparison frequently re-considered and 

 repeated, subsequently yielded, in much accordance with the 

 former, a total width in the line of the ship's course, of about 600 

 feet. 



4. But the total distance betwixt the crests of waves, then rec- 

 koned at 550 feet, a distance passed by the wave in 16'5 seconds 

 of time, by no means indicates, it is obvious, the real velocity of 



I the wave, as the ship meanwhile was advancing nearly in the same 

 ! direction at the rate of nine knots — that is, nine geographical 

 miles, or (6075-6 feet X 9 = ) 51,680-4 feet per hour, or 152 feet 

 per second. During the time, therefore, of a wave passing the 

 ship = 16-5", the ship would have advanced on its course 

 16-5 X 15-2 = 250-6 feet. Reducing this for the obliquity of two 

 points we have 231-5 feet to be added to the former measure, 559 

 feet, which gives 790-5 feet for the actual distance traversed by 

 the wave in 16-5 seconds of time, being at the rate of 



i ^ ' ° z= ^7,251-7 feet, or 3267 English statute miles 



V 16-5 I ' ' " 



per hour. To know how far this result is but proximate, it should 



* Tlie bnroiQeler on Sntiirday, a' 8 p.m., wa« at '.'9 .^0 ; at fi a m of Sunday it haj 

 fa le-t to -28-80, be.ng 1-2 inches in 10 hjurs At ti ^ m. ol the latter daj it liLd risen to 



3D' JO inciie^i. 



