170 



NATURE 



{Jan. I, 1874 



an exact fifth with each other ; and, on counting the 

 number of indentations contained in a given length of 

 each series, it appeared that for 30 of the lower sound 

 there were 45 of the higher, which numbers are in the 

 exact proportion (2 : 3), which connects the lengths of two 

 equally tense wires, giving that interval. Galileo, who had 

 felt a tremor pass from the chisel to his hand at each ex- 

 periment, inferred that what really determined a musical 

 interval was the ratio of the numbers of vibrations per- 

 formed in equal times by its constituent notes, and that 

 that ratio was inversely as that of the lengths of the wires 

 producing them. In order to bring out the crucial nature 

 of his experiment, he goes on to remark, with extreme 

 acuteness, that there was, prior to it, no reason for re- 

 garding the relations known to connect musical intervals 

 with the lengths of wires as in any exclusive sense repre- 

 senting such intervals. With equal propriety might the 

 ratio of the tensions under which two wires of equal 

 lengths emitted sounds forming an interval be taken as 

 its representative. In this case we should obtain the in- 

 verse square root of the ratio resulting from the former 

 mode ot comparison. Thus Galileo's experiment alone 

 supplied derisive ground for concluding that the relations 

 ol length between similarly circumstanced wires, likewise 

 governed those of period between corresponding aerial 

 vibrations. 



Prof. Tyndall, in referring to the above experiment, has 

 described it as performed " by passing a knife over the 

 edge ot a piastre " (" Sound," 2nd ed., p. 51). This is an 

 obvious mistake caused by incorrect translation. Galileo 

 was scraping " una piastra d'ottone," i.e., not "' a piastre," 

 but " a plate of brass." An excellent numismatist assures 

 me that the material mentioned is alone decisive of the 

 point, the piastre in Galileo's time being invariably made 

 of silver. Sedley TAYLOR 



THE HOOSAC TUNNEL 



THE following facts respecting the Hoosac tunnel, in 

 which the borings from east and west communi- 

 cated on Nov. 28, may prove of interest. The moun- 

 tain penetrated is part of the chain of mountains that 

 skirts, at a distance of two or three hundred miles 

 inland, the Atlantic coast of the United States ; of which 

 the Blue Ridge in Virginia, the Alleghanies in Penn- 

 sylvania, the Catskills and Adirondacks in New York, 

 the Green Mountains in Vermont, and the White Moun- 

 tains in New Hampshire, are prominent examples. 

 Hoosac Mountain has two summits, the eastern being 

 2,210, and the western 2,508 ft. above tide-water. 



The enterprise has been the subject of various under- 

 takings by different contractors, and the greater part of 

 the earlier work during the years from 1848 to 1863, in 

 length but one-twelfth of the whole distance, was on a 

 smaller scale than the subsequent plan adopted, and had 

 to be much enlarged and strengthened. The present 

 contract requires a clear width of bore of 24 ft. and a 

 height of 20 ft. ; the total length of the tunnel is 25,031 

 ft. A central shaft pierces it from above, at a distance 

 of 12,837ft. from the eastern, and 12,194ft from the 

 western portal. The shaft has a depth of 1,038 ft., and is 

 of elliptical form, its major axis is 27 ft. being coincident 

 with the line of the tunnel ; its minor axis is 15 ft. The 

 grade of the tunnel slopes up to the shaft from both ends, 

 with a rise of 26-,f| per mile. The shaft is not placed at 

 the lowest point between the two summits of the moun- 

 tains, as the exigencies of the work at the western ex- 

 tremity, and the presence of a stream of water at the 

 point of lowest depression, made a site half a mile nearer 

 the western portal preferable. The tunnel is 767 ft. above 

 tide-water at its extremities. The temperature within 

 averages 58° F. 



The total excavation is about 1,000,000 tons of rock., 



requiring somewhat over 1,450,000 days' work. The 

 boring was principally through mica schist, similar to 

 that of the surface. The miners found it lying on the 

 edge of the foliations and disposed to hang together after 

 the blast. They compared the operation of working in 

 it to pulling boards endwise from a pile of lumber. Rock 

 of this character was found continuous until a point was 

 reached within about 5,000 feet west of the central shaft. 

 At that point the proportion of mica was diminished and 

 the rock began to lose its foliated structure, becoming 

 more homogeneous or granitic. In fact it might be cha- 

 racterised in general terms as granite with the ingredients 

 differently proportioned at different localities, in some 

 places feldspar, in some mica, and in others quartz pre- 

 dominating. This rock was harder to penetrate with the 

 drills, but broke out more satisfactorily with the blast than 

 the mica schist. 



The chief trouble was occasioned by what received the 

 name of " demoralised rock." This was rock saturated 

 with water, which, exposed to air, disintegrated into mere 

 mud, rendering the support of masonry absolutely neces- 

 sary. The tunnel will not probably be ready for railway 

 traffic before next July, as there is yet much work to be 

 done, the total cost at that date, it is estimated, will not 

 fall short of 12,500,000 dols. 



NOTES 



On Monday last the French Academy of .Sciences named Mr. 

 J. Norman Lockyer, F.R.S., one of its Correspondents, to fill the 

 place rendered vacant in the Astronomical Section by the death 

 of Encke. We believe that the following is a complete list of the 

 English scientific members of the French Institute at the present 

 time : — Foreign Members — Prof. Owen, Sir C. Wheatstone. 

 Correspondents : Geometry — Prof. Sylvester. Meclianics — .Sir 

 \Vm. Fairbairn. Astronomy— Sir G. Airy, Mr. Hind, Prof. 

 Adams, Prof Cayley, Sir Thomas MacLear, Mr. Lockyer. 

 Geography and Navigation — Admiral Richards, Dr. Livingstone. 

 Physics — Dr. Joule. Chemistry — Dr. Frankland, Dr. William- 

 son. Mineralogy — Sir C. Lyell, Prof. W. 11, Miller. Botany — 

 Dr. Hooker. Anatomy and Zoology — Dr. Carpenter. 



At tlie meeting of the Paris Academy of Sciences, which took 

 place on December 22, the places of Correspondents in the 

 Physical Section, vacant by the death of M. Hansteen, and the 

 election of Sir C. Wheatstone to a foreign" associateship, were 

 filled up by the election of MM. Angstrom and Billet. 



Her Majesty's Commissioners have resolved to commence, 

 in connection with the series of international e.\hibitions, per- 

 manent collections which shall illustrate the ethnology and geo- 

 graphy of the different portions of the British dominions, and 

 ultimately form a great national museum of the empire upon 

 which the sun never sets. They will be arranged for the present 

 in the galleries of the Royal Albert Hall. Many portions of 

 the empire are inhabited by aboriginal races, most of which are 

 undergoing rapid changes, and some of which are disappearing 

 altogether. These races are fast losing their primitive charac- 

 teristics and distinguishing trails. The collections would em- 

 brace life-size and other figures representing the aboriginal in- 

 habitants in their ordinary and gala costumes, models of their 

 dwellings, samples of their domestic utensils, idols, weapons of 

 war, boats and canoes, agricultural, musical, and manufacturing 

 instruments and implements, samples of their industries, and in 

 general all objects tending to show their present ethnological 

 position and state of civilisation. It is proposed to receive for 

 the Exhibition of 1874 any suitable collections, which will be 

 grouped and classified hereafter in their strict ethnological and 

 geographicaljrelations. As, however, there ,is at present great 

 public interest in the various tribes inhabiting the West Coast Oi 



