A WEEKLY ILLUSTRATED JOURNAL OF SCIENCE 



" To the solid ground 

 Of Nature titists the mind tvhich builds for aye. " — WORDSWORTH 



THURSDAY, MAY 4, 1876 



TBE PROGRESS OF THE LOAN 

 COLLECTION^ 



THE investigation of the nature of those forces by 

 which the material world is ceaselessly being moved 

 and transformed, enlists in our day the energies of 

 a host of scientific workers. It would be hard, per- 

 haps, to mention a department of natural science for the 

 study of which a good knowledge of the fundamental 

 principles of what we now term physics is not at least a 

 valuable aid and qualification, if not indispensably requi- 

 site. To the geologist and the biologist, no less than to 

 the astronomer and the chemist, will such knowledge 

 seem imperative. Considering the widespread ramifica- 

 tions of this division of science, it is not wonderful that 

 the apparatus belonging to it should occupy so large a 

 share of the available space in the present collection. 



The remark formerly made, that much of the interest 

 awakened in this loan collection will centre in its histori- 

 cal element — in the primitive forms of apparatus that 

 represent, in some sort, the germs of some great develop- 

 ment of scientific thought — holds good for the depart- 

 ments of which we propose now to take a brief survey 

 in continuation of our last week's article. On entering 

 the room devoted to physics (exclusive of electricity 

 and magnetism), attention is drawn to some aged- 

 looking apparatus on the right. These are the cele- 

 brated original Magdeburg hemispheres of Otto von 

 Guerickd. They were exhibited by him in 1654 before 

 the Princes of the Empire and the foreign ministers 

 assembled at the Diet of Ratisbon. The force of two 

 teams, each consisting of a dozen horses, made to pull in 

 opposite directions (a portion of the rope is shown) was 

 insufficient to separate the exhausted hemispheres. It 

 was shortly after this date that the Burgomaster of Mag- 

 deburg heard of Torricelli's great discovery. The original 

 air-pump of Otto von Guerick^ is also exhibited. It con- 

 sisted of a globe of copper, with a stop-cock, to which 

 a pump was fitted. The pump-barrel was entirely im- 

 mersed in water to render it air-tight. The improvements 



' Continued from vol. xiii. p. 505. 



Vol. XIV. — No, 340 



in the air-pump by Boyle and Hooke, Papin, Hawks- 

 bee, and others, can be followed by the actual instru- 

 ments they made. Among modern improved methods 

 of producing a vacuum, is the pump of M. Deleuil, in 

 which the pistons are solid cylinders of considerable 

 length, without packing or lubricants, and not fitting 

 tightly in the tubes. The internal friction of the air in 

 the narrow space is so great that the rate at which it 

 leaks into the exhausted part of the vessel, is not com- 

 parable with the rate at which the pump is exhausting air 

 from the receiver. In the well-known air-pump of 

 Sprengel, air is drawn from the vessel to be exhausted 

 into a vertical tube, through the descent of small succes- 

 sive portions of mercury in the latter. Thilorier's appa- 

 ratus for liquefying carbonic acid, the apparatus used by 

 Dr. Andrews in his researches on continuity of the 

 gaseous and liquid states of matter, and a small model 

 of M. CoUadon's new air and gas compressor used for the 

 St. Gothard tunnel, may also be noticed here. 



The musical commencement of sound is generally put 

 at about thirty-two (single) vibrations, and the upper limit 

 of audition at about 73,000. Here will be found apparatus 

 illustrating both extremes ; including two organ pipes, 

 the individual sounds of which are inaudible, but whose 

 resultant tone or beat is within the limits of hearing. Helm- 

 holtz's double siren, and various other instruments con- 

 nected with his invaluable researches on sound, will repay 

 examination. Among musical instruments we may note 

 some models of ancient Egyptian pipes, from the British 

 Museum and that of Turin ; an enharmonic harmonium, 

 tuned according to the division of the octave into fifty- 

 three equal intervals ; and the first of the now generally 

 adopted upright pianofortes patented by Robert Wornum 

 in 181 1. Mr. Baillie Hamilton contributes a series of 

 apparatus illustrating very instructively the progress of 

 the ^olian principle. The velocity of transmission 

 of sound in water was experimented on by CoUadon, on 

 the lake of Geneva, in 1826, and again in 1841, and some 

 of his apparatus is shown in the present section. With 

 the long tube like a speaking trumpet, it is possible, in 

 calm weather, at the distance of more than a hundred 

 kilometres, to hear the strokes on a bell of half a ton weight 

 immersed in the water. Once more, the apparatus is to 



