514 



NATURE 



{April -so, 1874 



100 ft ., and that with a cloudy sky it is only half what it is with a 

 clear sky. These results were from the mean of his observations ; 

 under exceptional circumstances the variations were both greater 

 and less. It is hence shown that rays of sound otherwise hori- 

 zontal would be bent upwards in the form of circles, the radii of 

 which with a clear sky are 1 10,000 ft., and with a cloudy sky 

 220,000 f:., so that the refraction is double as great on bright 

 hot days as it is when the sky is cloudy, and still more under 

 exceptional circumstances, and comparing day witli night. 



It is then shown by calculation that the greatest refrac- 

 tion — 110,000 ft. radius — is sufficient to render sound from 

 a cliff 235 ft. high inaudible on a ship's decli 20 ft. high 

 at 1 5 miles, except such sound as might reach the ob- 

 server by divergence from the waves above, whereas wlien 

 the refraction is least — 220,000 ft. radius — or where the 

 sky is cloudy, the range would be extended at 2 J miles with a 

 similar extension for the diverging waves. It is hence inferred 

 that the phenomenon which Prof. Tyndall observed on July 3, 

 and other days— namely that when the air was still and the sun 

 was hot he could not hear guns and sounds from the cliffs of 

 South Foreland, 235 ft. high, for moie than two miles, whereas 

 when the sky clouded, the range immediately extended to three 

 miles, and as evening approached mucli farther, — was due, not so 

 much to stoppage or to reflection of the sound by invisible vapour 

 as Prof Tyndall has supposed, but to the sounds being lifted 

 over his head in the manner described ; and that had he been 

 able to ascend 30 ft. up the mast, he might at any time have 

 extended the range of the sound by a quarter of a mile at least. 

 Or had the instruments on the top of tlie cliff been compared 

 with similar instruments at the bottom, a very marked difference 

 would have been found in the distances at which they could be 

 heard. 



It seems that there were instruments at the bottom, and it is 

 singular that tliroughout his report Prof. Tyndall makes no 

 comment on their performance, unless they were at once found 

 to be so inferior to those at the top that no further notice was 

 taken of them ; this seems possible, since beyond mentioning th»t 

 they were there, Prof Tyndall throughout his report never refers 

 to them. 



It also seems that besides those results of Prof. Tyndall's experi- 

 ments, there are many other phenomena connected with sound, of 

 which this refraction affords an explanation, such as the very great 

 distances to which the sound of meteors has been heard as well 

 as the distinctness of distant thunder. When near, guns make a 

 louder and more distinctive sound than thunder, althouglt tliunder 

 is usually heard to much greater distances. In hilly countries, 

 or under exceptional circumstances, sounds are sometimes heard 

 at surprising distances. When tlie Naval Review was at Ports- 

 mouth, the volleys of artillery were very generally heard in 

 Suffolk, a distance of 150 miles. The explanation being that 

 owing to refraction (as well as to the other causes) it is only 

 under exceptional circumstances that distant sounds originating 

 low down are heard near the ground with anything like their full 

 distinctness, and that any elevation either of the observer or of 

 the source of sound above the intervening ground causes a corre- 

 sponding increase in the distance at which the sound can be 

 heard. 



SCIENTIFIC SERIALS 



Mcmorie dtlla Sociita degli Spectroscofis/i Italiani, February. — 

 Father Secchi contributes a p.aper On his Observations of Solar 

 Prominences from April 23 to October 2, 1S73. From his 

 tables it appears that the sun was observed on 127 days, when 

 1,052 prominences were seen, being more than 8 a day, the 

 maximum number visible on any one day was 13, and the mini- 

 mum 2. The greatest number of prominences over 64" high 

 occurred in lat. 30'' 40' N. and 20° 30' S. The greatest number 

 of prominences of all kinds were in lat. 20° 30' N. and 10° 20' S. 

 The same author also makes some remarks on the spectroscopic 

 observations of the transit of Venus. 



Astronomische Nachrichtcn, Nos. 1,980-1,981. — These numbers 

 contain a large quantity of observations of positions of the minor 

 pUnets and comets made in 1873 by Leopold Schulhof. He 

 also gives the positions of more than 100 variable stars, with re- 

 marks on a new variable position for 1850, R.\ 23° 10' 35" Dec. 

 — 19° 39'7. I'rof Peters gives the position of Planet 135, 

 Feb. 18, 1874, at I4h. 37m. 40s., Hamilton College, M.T., 

 RA iih. 19m. 4273. Dec. -f 4" 25' 5"'ii mag. G. Spoerer gives 



the positions of spots and prominences for February last. J. 

 Palisa gives the position ot the planet discovered by him on 

 March 18, 4h. 46m. 39s. RA I2h.22ni. 2'i2s. Dec. - 3° 19' 33"'4. 

 No. 1,982 contains a long paper On a Method of Computing 

 Absolute Perturbation, being in great measure similar to that of 

 Laplace. 



Journal of the Franklin Institute, March. — This number 

 contains an account, by Mr. Crew, of the '" prismoidal " one- 

 rail railway (of his invention), of which he has made two years' 

 trial in Alabama, with encouraging results. The cars are kept 

 securely on the prismoidal track by a combination of wheels ; a 

 centre one, at either end, on the rail, kept on the track by re- 

 volving flanged wheels at either side ; and wheels on the sides of 

 the prismoid, with strong wrought-iron bars to the side of the 

 car ; these keep the car upright. One proposed application of 

 the system is that of elevated rapid transit by steam through 

 crowded streets in populous cities. As to speed, Mr. Crew 

 thinks even 100 miles an hour would be possible ; there is no 

 oscillation through lateral motion. — Mr. Richards continues his 

 Principles of Shop Manipulation for Engineering Apprentices; 

 treating of belts, gearing, hydraulic and pneumatic apparatus as 

 means of transmitting power, and of " machinery of applica- 

 tion " of power. — Mr. Isherwood points out a method of ascer- 

 taining what portion of the feed-water admitted to a boiler is 

 entrained in the form of spray by the escaping steam. — Details 

 with reference to the Girard Avenue Bridge (which will form 

 the chief entrance to the West Park, at Philadelphia), are fur- 

 nished by Mr. liering. — Prof. Thurston claims for Count Rumford 

 a higher place in connection with thermo-dynamics than has 

 hitherto been assigned to him ; affirming that he first, and half a 

 century before Joule, determined with almost perfect accuracy 

 the mechanical equivalent of heat, while the sole credit of disco- 

 vering the true nature of heat is due to him. — We may note, in 

 addition, a paper On Railway Crossings and Turnouts, by Mr. 

 Evans, and one On the Sanitary Care and Utilisation of Refuse 

 in Cities, by Dr. Leas, who describes, more especially, the system 

 followed in Baltimore. 



SOCIETIES AND ACADEMIES 



London 



Royal Society, April 23. — On some points connected with 

 the Circulation of the Blood, arrived at from a study of the 

 .Sphygmograph Trace, by A. H. Garrod, B. A., Fellow of St. 

 John's College, Cambridge. 



The author commences by giving a table containing a fresh 

 series of measurements of the ratio borne by the cardiosystole * 

 to its component beat in the cardiograph trace. These tend 

 strongly to substantiate the law previously published by him, 

 viz. , that the length of the cardiosystole is coust.mt for any given 

 pulse-rate, and that varies as the square root of the length of the 

 pulse-beat only, being found from the equation .vy = 20\Jx when 

 .» = the pulse-rate and y = the ratio borne by the cardiosystole 

 to the whole beat. 



A similar series of fresh measurements are given in proof of the 

 law previously published by him, that in the sphygmograph 

 trace from the radial artery at the wrist, the length of the sphyg- 

 mosystolet is constant for any given pulse-rate, but varies as the 

 cube-root of the length of the pulse-beat, it being found from 

 the equation xy' — 47\^-»', where .v = the pulse-rate, and y' = 

 the ratio borne by the sphygmosystole to the whole beat. 



By measurement of sphygmograph tracings from the carotid 

 in the neck and posterior tibial artery at the ankle, it is then 

 shown that the length of the sphygmograph in those arteries is 

 exactly the same as in the radial ; so that the above-stated law as 

 to the length of the sphygmosystole in the latter applies to them 

 also, and must therefore equally apply to the pulse in the 

 aorta. 



Such being the case, by comparing the equations for finding 

 the length of the cardiosystole with that for finding the aortic 

 sphygmosystole, the relation between the whole cardiac systolic 

 act and the time during which the aortic \alve remains open 

 can be estimated with facility ; for by subtracting the shorter 

 sphygmosystole from the longer cardiosystole a remainder is 

 obtained which can be nothing else than the expression of the 



* The Citrdiosystolc is tlie interval between the commencement of the 

 systole and the closure of the aortic valve in each revolution. 



t The sphygmosystole is the inter\'al between the opening and closure of 

 the aortic valve in each cardiac revolution. 



