I found a book titled, “Fogs and Fog Signals of the Pacific Coast of the United States, Pub. for the use of shipmasters, owners, and agents interested in the commerce and navigation of the pacific coast (1888), ” that partially answers one of the mysteries that has been repeated in a number of my postings about shipwrecks. That mystery is, how could so many ship captains and crews swear they never heard the fog whistles when the lighthouse or signal keepers and nearby residents just as vehemently swore they had heard them continually? I had assumed exhaustion, drunkenness, dereliction of duty or insurance fraud was involved to some degree by one or both parties, in most of the incidents. Perhaps, that wasn’t the case, as the book seems to indicate. Perhaps, the heavy layers of fog our coast is subject to, and its effect on sound waves was, at least in some cases, the answer.
In the Coastside area there were three fog stations at the time the book was written, Ano Nuevo, Pigeon Point, and Montara, As you can see from the chart I’ve attached, as of July 1st, 1888, the Ano Nuevo station had been in service 11 years, 10 months, and the Pigeon Point and Montara station,11 years 11 months. During that slightly more then a decade all three stations had been operating the maximum during the month of September with totals of 1,671 total hours during that month for Ano Nuevo, 1,784 hours for Pigeon Point and 1,636 for Montara. That is about 1 out of 5 hours in that month. The minimum month for all of them was April, with 408, 385, and 412 hours respectfully, or between an an hour and an hour and a half a day.
At this time Ano Nuevo had a 12 inch steam whistle that sounded a blast for 10 seconds, followed by a 35 second quiet interval. Pigeon Point also had a 12 inch steam whistle that alternated between a 4 second blast, followed by a 7 second quiet interval, then followed by another 4 second blast, but followed by a 45 second quiet period. Being so close together, it was critical that a shipmaster could tell the difference between the two. Montara had a 5 second blast followed by a 23 second interval.
Later in the book I found mention of the problem of not hearing the fog whistle, even though it was sounding. It read:
“At this station, (Ano Nuevo) which is six miles south of Pigeon Point, some experiments have been made that indicate an area of inaudibility as existing not far from the whistle. The steamer Shubrick, in 1875-76, was run in three different directions from the whistle during the experience of fog, while the whistle was blown regularly all the time. Captain Korts, in charge of the vessel, says that in running in a northwest direction straight from the signal and to the windward, the sound was heard up to the third mile, and then lost, regained at four miles distance. In running southeast–i.e. with the wind– the sound was lost near the second mile and was not heard again until the fourth mile was reached. In moving straight out from shore, in a southwest course, the sound was heard continuously for the whole four miles. The fog in those trials did not reach above 150 feet above the surface of the ocean, and upon going to the masthead Captain Korts, found that immediately over the signal it was swelled up in an unbrella-like shape, and was very thin at the summit of this dome, the steam of the whistle showing through it.
These experiments, as well as the experience of Capt. Whitelaw already quoted, indicate that when sound signals are generated in one medium, whether that be a clear atmosphere, or more or less dense fog, the sound waves have great difficulty in passing from that media to another.”
Captain T.H. P. Whitelaw, who for many years had had the occasion to note the audability of sound signals on this coast while affording relief to wrecked vessels and recovering material from such, had said: “Clear spaces in fog banks alter or interrupt the course of the sounds of signals. When sound strikes the thick strata it is deflected upward–sent overhead– and so lost; and when it passes into lighter strata or open spaces it is heard again”
As an illustration of this phenomena he drew this diagram and explained it as follows:
“Approaching Point Bonita, and when about 6 miles distant (A) I have met a wall of fog and could hear the siren on the Point plainly. Passing through this I have encountered a clear space (B) in which the siren was not heard. The fog seemed to arch overhead, touching the sea again at (C) about 3 miles from the Point. Here the siren was heard again and as soon as we passed into the open space (D) it was heard but faintly, and wholly lost when within about a mile and a half of the Point.”
He goes on with more diagrams and observations, but I think his point is made. The book ends with a whole list of conclusions that the shipmaster should not make about where there ship was, based on what they did or did not hear from a fog signal station. The paranoia that I would have felt after reading them would have made me a permanent landlubber back then, especially if I had to navigate anywhere there was fog, particularly at night.
While modern instruments have made many of these matters moot, if you want to know more about the dangers they faced, even after the great improvement of having fog stations built on previously even more treacherous coasts, Archive.org, has another book you might want to read. It was written in 1881 and is titled, “Aberrations of Audability of Fog Signals.” It documents how boats had run ashore an eighth of a mile from a fog whistle station and never heard it, and explains why. Somehow Sea Serpents seem less scary now. Enjoy. John
Just happened by your webpage featuring my story and noticed that I had mentioned mom was an artist and it occurred to me that since I have one of her paintings, I should take a pic and send it to you for inclusion if you so desire.
I also took, and am including, a photo of one of my Galen Wolf paintings
a beautiful rendition of a spot long gone on the Napa River. I hope you can use them.
hope you saw my friend kevon cottrell’s band, ‘blame it on the dog’, playing on spruce street during the pumpkin festival. i do miss that part of hmb — had a booth [stained glass, of course] in the early days. nostalgia hits me again when i see photos of the old rupert taylor building — used to stand on the upper veranda outside my ‘vision quest studio’ space
Here is a followup article about the San Pedro road modernization and realignment from the June 1937 issue of “Highways and Public Works.” that I sent you previously. It appeared in the December 1937 issue.
OCEAN SHORE HIGHWAY JOB IS COMPLETED
On Armistice Day November 11th, 1937, one of the most difficult highway construction projects, and probably the most important section of the so called, “Ocean Shore Highway,” between San Francisco and Santa Cruz, was opened to public travel.
District Construction Engineer E. G. Poss, in an article appearing in the June 1937, issue of this magazine, briefly described the nature of, and a few of the construction problems on this project. Accompanying the referred-to article was a sketch map showing the alignment, and a photograph of the former county road with its 250 curves, and 42.2 complete circle-turns in its 10.6 miles of length, with a total rise and fall of 2,409 feet.
The importance of this portion of the Ocean Shore Highway, commonly referred to as the “Pedro Mountain” section, was aptly portrayed by the twenty-eight curves involving only 3.8 circle turns and 1,225 feet of rise and fall of grade in the new 5.9 miles covered in this construction project.
TIME AND DISTANCE SAVED
The savings of 4.7 miles in distance does not truly reveal the convenience afforded the traveling public afforded by this new road. The former road, in practically its entire length, gave no sight distance to the motorist, who, in averaging fifteen miles per hour, throughout the entire length, was making good progress. The highway will permit progress throughout its entire length speeds averaging close to the legal speed limit of 45 miles per hour, and will effect a saving in travel time more then one-half hour to all motorists destined to south of Farallone City.
This highway will therefore assume great importance, not only as a recreation road between San Francisco and the beaches and redwood-covered slopes of the Santa Cruz Peninsula, but also an market artery in the transportation of truck garden, dairy, and stock-raising products of the rich agricultural area centering around the coast towns of HalfMoon Bay, Pescadero, Tunitas and San Gregorio.
The scenic nature of the new highway is portayed by the cover-page photograph on this magazine, which shows it to be comparable in this respect to the newly-opened Carmel-San Simeon scenic coast route.
From a construction standpoint, the project involved one and one-half million cubic yards of roadway excavation, or an average of one-quarter million cubic yards per mile. These quantities include approximately 700,000 cubic yards of material removed outside the original typical roadway section, principally slides occurring at the famous “Devil’s Slide” on Pedro Mountain, near the center of the project. Some daylighting of small cuts was included at vantage points, to give the motorist full advantage of the marine view, and to increase the sight distance as a safety precaution.
Rubble masonry walls played an important part in retaining the roadbed at control points on the steep mountain slopes. These were constructed in preference to concrete walls, due to the availibility of rock, from the standpoint of economy of construction, and also to keep the nature of the improvement in line with the scenic features of the rugged coast country traversed. Approximately 700 feet of lineal rubble masonry parapet walls were constructed on top of the masonry rubble retaining walls supporting the roadbed, a job itself. As is so common in the north coast section of northern California, where all formations have been shaken and disturbed in earthquakes in the past, providing stability of the roadbed calls for the solution of more difficult problems in the construction of large fills then it does in excavating the material from large cuts. The present project presented a problem in the construction of a fill approximately 85 feet depth at the centerline, involving approximately 100,000 cubic yards of material in place.
Within a length of 400 feet along the roadway, it was necessary to strip approximately 4,000 cubic yards of unstable top soil, and to excavate trenches twelve feet in width, and up to 20 feet of depth, involving approximately 12,000 further cubic yards of excavation.
These trenches, consisting of one transverse, two longitudinal, and one diagonal ditch, explored the natural drainage courses of a number of underground springs, and were led into one outlet trench and backfilled with large rock placed directly on the supporting rock, to insure the free drainage of the entire area beneath this important fill. Approximately 9,000 cubic yards of rock were placed in these trenches prior to the starting of construction on this fill.
Another special construction problem of providing a stable roadway was presented at a location where the typical section lay almost entirely in excavation. The roadway section, for approximately 150 feet in length, was trenched into the mountain side, but the slopes down the roadway were so steep and were of such unstable material that it was considered necessary to excavate to a maximum depth of up to 40 feet below grade on the lower side, to trench the mountain slopes and carefully rebuild the fill to grade, entirely out of large rock anchored into a stable portion of the mountainside.
In spite of all the precautions taken from an engineering standpoint to provide a stable roadway, as free as possible from major slides both in cut and fill sections, it is anticipated that considerable trouble will be experienced by our maintenance forces in the next two or three winters, in keeping the roadway clear of minor slides and the natural sloughing of material from the steep mountain slopes.
The maximum slide occurring on this project during construction broke on a point about 600 feet (measured horizontally) and approximately 500 feet (mesured vertically) from the grade of the roadbed. At this same point, the roadbed is approximately 330 feet above the ocean waters, with a slope below the road to the ocean.
Granfield, Farrar, and Carlin were the contractors, H.A. Simard was the resident engineer for the State on this project.