182 ANNUAL OF SCIENTIFIC DISCOVERY. 



A NEVT FORM OF MERCURIAL BAROMETER. 



M. dc Cclles has exhibited to the Academy of Sciences, of Paris, a mercu- 

 rial barometer, constructed under his direction. The barometer is the instru- 

 ment of Torricelli, with the following modifications : 1st, the diameter of the 

 barometric chamber is increased in proportion as it is desired to make the 

 instrument more sensitive; 2d, the cistern is replaced by a horizontal tube 

 0'15 ins. or 0'2 ins. in diameter, and of a length proportionate to the sensi- 

 bility of the instrument. The instrument has the form of a square. Slight 

 variations of the height of the vertical column correspond to considerable, 

 but always proportional movements of the horizontal leg. This ratio is in- 

 versely as the squares of the diameters. An index of iron, placed in the 

 horizontal tube, is pressed outward while the pressure of the air is diminish- 

 ing, and is left when the column returns. It marks the minimum pressure, 

 and may be brought back by a magnet. M. de Celles claims for this instru- 

 ment the three advantages : 1st, of very great sensitiveness. 2d, a constant 

 level. 3d, a minimum index. 



ON THE HEIGHT OF THE ATMOSPHERE. 



A letter from Mons. Emm. Liais, published in the Comptes Rendus (Jan. 10, 

 1859, p. 109), gives the results of his inquiries into the height of the atmos- 

 phere, as deduced from observations on polarization made at the tropics at 

 the commencement of dawn and the end of twilight. The letter -is dated 

 San Domingo, Bay of Rio Janeiro, Dec. 6, 1858. His observations at that 

 place, Dec. 1st, 2d, and 3d, indicated that the limit of atmospheric polariza- 

 tion was 9' 40" in passing from 20 3 east of the zenith to 20 D west; but at San 

 Domingo, of which the latitude is 23 S., the limit of the shadow passes over 

 25.6 kilometres per minute, or 247'5 kilometres in 9' 40''. From this the 

 height of the atmosphere is calculated to be 340 kilometres, or 211 miles. 



THE PHONAUTOGRArH. 



At the last meeting of the British Association, the Abbe Moigno read a 

 paper describing a new method of reproducing the human voice and other 

 sounds in such a manner as to be visible to the eye. The instrument by 

 which this is effected is called the phonautogi-aph, and is the invention of a 

 young Frenchman, M. E. L. Scott. The phonautograph consists of a tube, 

 enlarged at one end in the same manner as a trumpet, in order to concen- 

 trate the sounds, which arc conveyed through it to a thin membrane tightly 

 strained over the other end of the instrument. This membrane carries 

 affixed to it an excessively light style or pencil, which is put in motion by 

 every vibration produced by the action of the air upon the membrane. Be- 

 hind this style a band of paper, covered with lampblack, is unrolled by 

 clock-work; and as this band passes along, the point of the style traces upon 

 the lampblack all the curvilinear and rectilinear movements originating in 

 the vibrations of the membrane, and thus it produces, in its own peculiar 

 characters, a faithful reproduction of the sound. 



M. Moigno also exhibited a collection of sheets of paper, on which were 

 self-registered the sounds of the human voice, organ-pipes, etc., to the 

 amount of five hundred or a thousand vibrations. This continued cnregis- 

 tration forms an uudulatory curve, so perfectly and distinctly traced that the 



