114 



NA TURE 



[May 30, 1889 



■experiments was undertaken, by a commission appointed by the 

 Lighthouse Board of the United States, to determine the relative 

 powers of various fog signals which were submitted to the notice 

 •of the Board. In 1872, a Committee of the Trinity House, with 

 the object of ascertaining the actual efficiency of various fog 

 •signal-; then in operation on the North American continent, 

 visited the United States and Canada, where they found in 

 service, DaboU's trumpets, steam whistles, and siren apparatus, 

 sounded by steam and compressed air ; these latter apparatus 

 were devised by Mr. Fc-lix Brown, of Progress Works, New York ; 

 and from the report of the Trinity Elouse Committee, it does not 

 appear that they were greatly impressed with this instrument, 

 "but probably they had not an opportunity of testing its real 

 merits as compared with other signals. The late Prof. Henry, 

 of ths United States Lighthouse Board, entertained a very 

 high opinion of the siren ; and on his advice, and the urgent 

 recommendation of Prof. Tyndall, one of these instruments was 

 sent to England, and included in the fog signal experiments 

 at the South Foreland in 1873-74. This investigation was 

 -carried out by the Trinity House, with the view of obtaining 

 xlefinite knowledge as to the relative merits of various sound- 

 producing instruments then in use, and also of ascertaining how 

 the pro,)agation of sound is affected by meteorological phenomena. 

 Prof Tyndall, as scientific adviser of the Trinity House, con- 

 ■ducted the investigation, aided Ijy a Committee of the Trinity 

 House, and their engineer. These experiments were extended 

 over a lengthened period, in all conditions of weather, and the 

 ■well-known scientific and practical results obtained, together 

 with the ascertained relative merits of found-producing instru- 

 ments for the service of the mariner, have proved to be of the 

 highest scientific interest and practical importance. The in- 

 vestigation at the South Foreland was followed up by the 

 Trinity House with further explosive fog signal experiments, 

 in which they were assisted by the authorities at Woolwich 

 Arsenal with guns of various forms, weight of charges, and 

 descriptions of gunpowder. The powders tested were (i) fine 

 grain, (2) larger grain, (3) rifle large grain, and (4) pebble. The 

 result placed the sound-producing powers of the-e powders 

 exactly in the order above stated ; the fine grain, or most rapidly 

 burning powder, gave indisputably the loudest sound, while the 

 report of the slowly burning pebble powder was weakest of all. 

 Here again the greater value of increased rapidity of combustion 

 in producing sound was demonstrated. It was found that charges 

 of gun-cotton yielded reports louder at all ranges than equal 

 charges of the best gunpowder ; and further experiments proved 

 that the explosion of half a pound of gun-cotton gave a sound 

 equal in intensity to that produced by three pounds of the best 

 gunpowder. These investigations led the Trinity House to 

 adopt gun-cotton for fog signals at isolated stations on rocks 

 and shoals, as already described, where, from want of space, 

 nothing better than a ball, or gong, it had hitherto been possible 

 to apply. Of all the sound signals now employed for the 

 warning and guidance of mariners during fog, viz. bells, gongs, 

 guns, whistles, reed trumpets, sirens, and sounds produced by the 

 explosion of gun-cotton, the blasts of the siren and explosions 

 of gun-cotton have been found to be the most efficient for coast 

 fog signals ; therefore these signals have received the greatest 

 care and attention in their development. The siren doubtless 

 ranks first for stations wherever it can be applied, chiefly on 

 account of its economy in maintenance, and the facility it affords 

 for giving prolonged blasts of any desired intensity or pitch, 

 and thus providing any number of trustworthy distinctive 

 characters that may be required to insure individuality in the 

 signal. Sirens are now employed at many floating and shore 

 stations of the Trinity House ; and one, recently installed at 

 Saint Catharine's Lighthouse, Isle of Wight, of the automatic 

 Holmes type, of which we have here a model, absorbs during its 

 blasts not less than 600 horse-p:)wer. The audibility of the blasts 

 of this instrument may be considered to be trustworthy at a range 

 of two miles under all conditions of foggy atmosphere, on the 

 sea surface, over which it is intended to be sounded. It is very 

 desirable that for many landfall stations a greater trustworthy 

 range be provided for the mariner, but this can only be afforded 

 by such increased power as would be required for a more 

 powerful electric light installation, to serve the mariner in other 

 gradations of thick atmosphere. A very important improvemant 

 and economy has lately been effected in the sirens of the Trinity 

 House, by rendering them always instantaneously available for 

 sounding at their maximum power. This is accomplished by the 

 storage of a sufficient quantity of compressed air, at a pressure 



considerably above that required for sounding, to work the siren 

 during the time required for raising steam and starting the 

 engine. The signal is thus always in readiness for immediate 

 action day or night, with an expenditure of fuel only incurred 

 during fog, which fortunately on the coast of this country does 

 not exceed an average of 440 hours per annum. The experience 

 yet gained with the most powerful fog signals now in use, although 

 these apparatus far exceed in efficiency for the service of the 

 mariner in fog any light that science can provide, is not yet 

 so satisfactory as we could desire. The best signal is, as I have 

 already stated, occasionally not heard, under certain atmospheric 

 conditions, beyond two miles ; while under other conditions, 

 not apparent to the mariner, the signal is distinctly audible 

 at ten miles ; therefore there is much to be desired in the 

 development of the means of propagating sound waves, and in 

 rendering [hem audible to the mariner. In conclusion I would 

 venture to state that, with the best light and sound signals that 

 can be provided, there are conditions of the atmosphere in which 

 the mariner will earnestly look and listen in vain for the desired 

 light or sound signal, and he must s'.ill, under such circumstances, 

 exercise caution m availing himself of their guidance, and never 

 neglect the assistance always at hand of his old trusty friend 

 the lead. 



PRELIMINARY REPORT OF THE NEWALL 

 TELESCOPE SYNDICATE.^ 



A T the end of the Lent Term the Syndicate met for the first 

 time and drew up a Report to the Council of the Senate, 

 recommending that a Committee of exjierts .--hould go to Gates- 

 head to view Mr. Newall's telescope and report on its condition 

 and capabilities. A letter of acknowledgment was also sent to 

 Mr. Newall thanking him for his generous offer. 



In consequence of their recommendation, Mr. Christie, Astro- 

 nomer Royal, Mr. Common, F.R.S. , and Mr. Graham, First 

 Assistant at our Observatory, went to Gateshead and made a 

 thorough examination of the telescope and of its accessories. 

 They reported to the Syndicate as follows : — 



Report on Mr. Ne'valfs 2^-Jnck Refractor. 

 We the undersigned, being the Committee appointed by the 

 Newall Telescope Syndicate to inquire into and report on the 

 condition and capabilities of the above in-trument, beg to submit 

 the following report as the result of an examination made on 

 March 28 and 29. For convenience of reference we have divided 

 the report under three heads : — 



1. On the present condition of the telescope and dome. 



2. On the necessary work to be done in removing and re- 

 erecting, to put the whole in an efficient state. 



3. The capabilities of the instrument when re-erected. 



I. On the evening of March 28, the sky being overcast, the 

 quality of the object-glass was tested by a'tificial stars, formed 

 by the light of a lamp shining thr )ugh holes in a metal screen, 

 placed at a distance of about 1500 yards. The result of those 

 tests, which it is unnecessary to specify more fully, was sufficient 

 to enable the Committee to come to the conclusion that the 

 object-gla'ss is a remarkably fine one, entirely free from any 

 defect. On the conclusion of those tests about midnight, and as 

 the Committee were about to leave, the sky cleared to a slight 

 extent, and at intervals the telescope was turned upon some stars 

 and upon Saturn. Owing to the state of the atmosphere, the 

 definition was very variable, but the Committee saw enough to 

 confirm them in the opini'^n they had already formed as to the 

 excellent quality of the object-glass. During these examinations 

 and tests the mounting showed itself to be extremely steady and 

 quite free from vibration. On the morning of the 29th the 

 Committee again met at Ferndene to complete the examination 

 of the instrument and dome by daylight. The telescope is no 

 doubt so well known that it is not necessary to state further than 

 that it is a first-class instrument, mounted on the plan of the 

 elder Cooke, and that it is fully provided with all the necessary 

 appliances to make it an extremely convenient and easily 

 managed instrument. 



The condition is such that the necessary cleaning, painting, 

 lacquering, &c. , more fully described in the next section, will not 

 be an expensive matter. 



The dome and substructure were next inspected. From i\ 

 brick wall, which rises to a height of about 2 feet, the whole a 

 of iron, the various parts, including the dome, being bolte 

 ' Rrp-in^fd from the Cambridge Unhiersiiv Kc/ort^r, May :i. 



