NATURE 



{May 4, 1876 



be seen by which Prof. Tyndall recently illustrated the 

 reflection of sound by heated air or vapours ; these, being 

 made to stream up through six openings in the long 

 chamber through which the sound is directed, are effectual 

 in stopping its progress. 



Of historical interest in the section of Light are 

 some early stereoscopes, comprising that of Sir David 

 Brewster ; a camera- obscura said to have belonged to 

 Sir Joshua Reynolds (which, when closed, has the form 

 of a large folio leather-bound book), the original form of 

 Brewster's kaleidoscope made by Bate, in 1 8 15, the first 

 heliostat, invented by Gravesande, &c. The vigour of the 

 young science of spectroscopy is indicated by the fine 

 array of instruments belonging to it, constructed by 

 Steinheil, Browning, and others. There is shown the 

 spectroscopic apparatus which Sir John Herschel used 

 in photographing actions of different parts of the 

 spectrum, and in his investigations on some supposed 

 new elements. For illustrating the theoretical side of the 

 subject of polarised light, various forms of instrument 

 have been devised, the most comprehensive of which is 

 known as the wave machine of Wheatstone ; its object is 

 to exhibit the results of the combination of various kinds 

 of vibration meeting at various phases. Instruments 

 based on the three different methods of producing plane 

 polarisation are exhibited ; and the various phases of 

 rotatory and other polarisation can be shown simulta- 

 neously by means of an instrument which was invented 

 independently by M. Mach and Mr. Spottiswoode. It is 

 known that Wheatstone invented a " polar clock," based 

 on the fact that the light from certain parts of the sky is 

 polarised, and the plane of polarisation depends on the 

 position of the sun ; this is included in the collection. 

 It would take too long to refer in detail to the now nume- 

 rous varieties of photometric apparatus, or the apparatus 

 for observing phosphorescence, fluorescence, and other 

 phenomena connected with light. Several specimens 

 exhibited of the enigmatical radiometers recently devised 

 by Mr. Crookes will doubtless excite lively interest and 

 speculation. In the photographic collection is the first 

 known photograph on glass, taken on precipitated silver 

 chloride by Sir J. Herschel ; also the second daguerreo- 

 type obtained by Daguerre in 1839. The Woodbury 

 and other processes are fully illustrated. 



In the Heat department we cannot allow ourselves to 

 linger at the fine collection of thermometric and other 

 instruments. Among them is a milligrade thermometer, 

 in which the interval between the freezing and boiling 

 points of water is divided into one thousand degrees ; it 

 obviates the use of fractions. Wedgwood's pyrometer 

 and Lavoisier's calorimeter are here ; and many will feel 

 interested in such apparatus as that by which Tyndall 

 conducted researches on radiant heat, Regnault, De la 

 Rive, and Marcet on the specific heat of gases, or Favre 

 and Silbermann on the heat disengaged in combustion. 



In the room devoted to Chemistry we come upon some 

 old apparatus which is of the simplest and even the 

 rudest character ; it is a part of that with which John 

 Dalton carried on his classical researches. Most of it 

 was made with his own hands, and the articles here 

 exhibited are chosen as illustrating this fact, and as indi- 

 cating the genius which, with so insignificant an equip- 

 ment, was able to produce such great results. The study 



of pneumatic chemistry was much advanced by the 

 experiments of Black and Cavendish. Black showed 

 that the difference between the caustic and mild alkalies 

 was that the latter contained^ArrtT air, a kind of air iden- 

 tical with that obtained from fermenting liquids. Caven- 

 dish pointed out the difference between inflammable air, 

 which we now call hydrogen, and fixed air, now known 

 as carbonic acid gas. Black's pneumatic trough and 

 balance, and Cavendish's balance, are among the col- 

 lection. The latter is rude in exterior but of singular 

 perfection. Here, also, is the balance, belonging to the 

 Royal Institution, which was used by Young, Davy, and 

 Faraday. The researches of Faraday on the conden- 

 sation and liquefaction of gases are well known, and one 

 may here see the apparatus he employed, along with a 

 number of the original tubes containing gases which he 

 liquefied. Thomas Graham's apparatus, also exhibited, 

 is remarkable, like that of Dalton, for the contrast be- 

 tween its simplicity and the great results that were 

 achieved by means of it. The amateur or professional 

 chemist will doubtless receive not a few happy hints in 

 inspection of the large variety of apparatus connected 

 with qualitative and quantitative analysis ; and the com- 

 prehensive collection of chemicals contains many novel- 

 ties. We further note some of the apparatus that Messrs. 

 Lawes and Gilbert have used in their important re- 

 searches in agricultural chemistry, and they exhibit a 

 case of casts of white Silesian sugar-beet illustrating the 

 influence of different manures on the amount of produce 

 and on the percentages of dry matter and sugar in the 

 roots. The great chemical industries of this country, in 

 fine, are well represented by models of manufactories 

 and by products. 



Coming to Biology, we may notice first an interesting 

 collection of old microscopes. Here is the silver micro- 

 scope that was used by Anthony von Leeuwenhoek, the 

 Dutch philosopher, and probably made by him ; also the 

 microscope used by Sir W. Hooker,in his description of the 

 British Jungermannieae, &c. The microscopes of Dawson 

 Turner, Robert Brown, Muschenbroek, and others, are also 

 included. There is a compound microscope invented 

 and constructed about the year 1590, by Jansens, the 

 inventor of the telescope. This object, with its tin tube, 

 is one of the most interesting things in the Collection. 

 It is instructive to compare these instruments with their 

 modern neighbours, of which there is a large variety. 



The older physiologists obtained only qualitative re- 

 sults from their experiments ; but the present generation 

 has witnessed a remarkable advance in the application of 

 instruments of precision to the quantitative determination 

 of the effects of physiological processes. From this point 

 of view a singular interest attaches to the muscle balance, 

 constructed and used just forty years ago, by the eminent 

 anatomist and physiologist who laid the foundations of 

 animal histology. It is intended to demonstrate that 

 muscular contraction takes place in accordance with the 

 laws of elastic bodies, and it may be regarded as the first 

 of the class of instruments referred to. The department 

 contains a rich collection of such instruments ; and no 

 better illustration could be taken than the apparatus by 

 which M. Marey has so successfully investigated the 

 phenomena of animal locomotion and other physiological 

 movements. The study of physiological optics has been 



