January 5, 1294 | 
SCIENCE. 
PusiisHED BY N. D. C. HODGES, 874 Broapway, New York. 
SUBSCRIPTIONS TO ANY PART OF THE WORLD, $3.50 A YEAR. 
To any contributor, on request in advance, one hundred copies of the issue 
containing his article will be sent without charge. More copies will be sup- 
plied at about cost, also if ordered in advance. Reprints are not supplied, as 
for obvious reasons we desire to circulate as many copies of SCIENCE as pos- 
sible. Authors are, however, at perfect liberty to have their articles reprint- 
edelsewere. For illustrations, drawings in black and white suitable for 
photo-engraving should be supplied by the contributor. Rejected manu- 
scripts will be returned to the authors only when the requisite amount of 
postage accompanies the manuscript. Whatever is intended for insertion 
must be authenticated by the name and address of the writer; not necessa- 
rily for publication, but as a guaranty of good faith. We do not hold our- 
selves responsible for any view or opinions expressed in the communications 
of our correspondents. 
Attention is called to the ‘‘Wants’’ column. It is invaluable to those who 
use it in soliciting information or seeking new positions. The name and ad- 
dress of applicants should be given in full, so that answers will go direct to 
them. The “Exchange” column is likewise open. 
THE CRUISE OF THE CLOVER—FURTHER RE- 
MARKS ON THE ABERRATIONS OF AUDIBILITY 
OF FOG SIGNALS—THE METHODS USED.* 
BY ARNOLD BURGES JOHNSON, WASHINGTON, D. C. 
Ir is now about a quarter of a century since Prof. 
Joseph Henry, the first President of this society, com- 
menced his investigation into the operations of the laws 
of sound in connection with the fog signals used by the 
Light House Board, of which board he was then the 
scientific member. 
When I was made Chief Clerk of the Light House Board 
in 1869 it became my duty, as well as a privilege which I 
highly prized, to act to a certain extent as his amanuensis 
and aid in putting the results of his experiments in the 
form of reports to the Light House Board. In this way 
I became interested in this work and was, in a very 
humble way, associated with Professor Henry in its pros- 
ecution. Thus I entered with him into a practical dis- 
cussion of the subject and became, after a fashion, pos- 
sessed of his views as to the best way to follow up the 
investigation. I thus came to know something of his 
tentative plans and of his desire to make very practical 
use for light house purposes of the outcome of the in- 
vesffgations. 
On Nov. 6, 1880, the great Long Island Sound steamer 
Rhode Island was stranded and finally lost on Bonnet 
Point in Narragansett Bay. Then, putting it roughly, a 
million in property was lost and thousands of lives were 
imperilled. The master and pilot of the steamer claimed 
that the fog-signal at Beaver Tail Point, about one and 
seven-eighths miles away, was not sounding at the time 
of the accident; and hence the casualty. The light 
keeper who was in charge of the fog-signal at the time, 
and who was in peril of losing his place, proved con- 
clusively that at the time of the wreck the sound of the 
fog-signal was heard at Newport, five miles away, at Fort 
Adams, four and a quarter miles away in one direction, 
and at Narragansett Pier, four and a half miles away in 
another direction. The steamer people, who were in 
danger of forfeiting their licenses, came back with affi- 
davits of many on board that they were anxiously listen- 
ing for the fog-signal, and that it was not in operation, 
for they did not hear its sound. 
Then the Light House Board took a hand in the mat- 
ter. It had been shown by Professor Henry that, although 
a sound could be heard at a certain distance from its 
1Read before the Philosophical Society of Washington, Nov. 25, 1893. 
SCIENCE. 3 
source, it might not be heard in the same direction, and 
at the same time, at a less distance. Could this be one 
of those cases? A naval officer in the service of the 
board, now ranking as a Commodore, was sent to the 
locality to find out. He had the fog-signal at Beaver 
Tail started, and cruised round it in a sail boat for some 
time, taking constant note of the intervals of the sound. 
He found, and reported to everybody’s surprise, that not 
only did he fail to get the sound of the Beaver Tail fog- 
signal at Bonnet Point, one and seven-eighths miles away, 
where the Rhode Island was lost, but he failed to get it 
at other points even nearer to the fog-signal, while he 
heard it on the same day at different points farther away, 
and much farther away in a line with the nearer points 
where he could not hear it. This settled the question. 
The light keeper was relieved from the charge of failing 
to have the fog-signal in operation, and the steamer 
people were relieved from the charge of failing to act on 
the warning of the fog-signal, which was blowing, but 
which, while within earshot, they might not hear. 
In 1881 the great propeller Galatea, while on the way 
from New York to Providence, ran onto Little Gull Island 
in Long Island Sound, imperilling many lives and much 
property. ‘There was, and is, on that island, which is but 
one-eighth of amile long, a powerful light and a powerful 
fog-signal. That fog signal has been often heard sixteen 
miles away. The defense of the steamer people was that 
the fog was dense and that the fog-signal was not blow- 
ing. The light-keeper, in his defense, showed that the 
fog-signal was blowing, that it was heard and noted at 
several different points in different directions, say at New 
London, Mystic, and at several light houses, many miles 
away, at the very time the Galatea ran on the little islet 
on which the fog-signal was at work. Again the Light 
House Board was required to look into the matter. 
Again careful investigation was made. And again it was 
shown that the fog-signal might be heard far off, 
and not close to, and the spots where it was not heard 
were noted and plotted on the chart; and again the 
steamer people and the light house people were exoner- 
ated from blame. 
In 1881 I gathered these facts and submitted them to 
the Philosophical Society. My paper was printed in the 
Bulletin of the Society, and it was largely copied in mari- 
time and scientific publications in this and other coun- 
tries. The light house establishments of England, France 
and Spain reprinted the paper, each in its own language. 
And the eminent Emile Allard, head of the French light 
house establishment and a prominent officer of the French 
Corps of Engineers, plotted my numerical statement of 
the intensity of sound as heard from the fog-signals, in 
eraphic form, that is, in lines of various width, and sent 
his diagrams to me in a letter in which he discussed the 
subject at length. 
The Light House Board meantime was considering the 
matter from a purely practical standpoint. If, it was 
reasoned, there is a point within earshot of a fog-signal, 
where, from any cause, the fog-signal cannot be heard, 
then some other signal should be placed at that point, 
from which vessels can take a fresh departure. Acting 
upon that idea, investigation was made as to the region 
about each prominent fog-signal which it had been said 
could not be heard at points where it ought to be heard. 
In several instances I was sent to such points to make in- 
vestigation and to report with recommendations. In the 
summer of 1885 I cruised about Point Judith, R. L, and 
the southeast end of Block Island, both at the entrance 
of Long Island Sound, and about the light house and fog- 
signal on Little Brewster Island, entrance to Boston 
Harbor. An area of silence was found and plotted about 
one and a quarter miles south of Point Judith, where the 
