November 23, 1893] 



NA Tl RE 



83 



and two concave mirior?, adjustanle automatically to minimum 

 deviation for any wave-length. The gases examined were air, 

 oxygen, carbon dioxide, and steam. Only the last two gave 

 positive results, some small deflection in the first two being due 

 to slight traces of moisture. Carbonic acid showed a very sharp 

 maximum far in the infra-red. The bolometer strip was to > 

 broad to determine whether it was a line or a band, but it is 

 most probably a somewhat ill-d-fined line. Steam showed 

 about ei^ht maxima, which must be described as bands. A 

 comparison of the spectrum of the Bansen flame with that of the 

 hot products of combustion arising from it showed that the 

 spectra obtained are similar and of a'most equal intensity ; so 

 that it is very probable that the spectra of hot gases are chiefly 

 due to temperature, and not to chemical action. A curious 

 and hitherto unexplained observation is that of a slight shifting 

 of the maxima towards the more refrangible end of the spectrum 

 when the temperature is lowered. 



To determine correctly the values of the critical constants of 

 a substance is a matter of considerable difficulty : the estimation 

 of the critical temperature, however, is generally believed to he 

 both expeditious and accurate. The usual method of taking 

 an observation of the critical temperature consists in heating 

 the liquid in contact with its saturated vapour in a closed space 

 to a temperature above th^ critical temperature, allowing the 

 substance to cool, an 1 noting the temperature tc at which the 

 meniscus of the liquid just appears in the misty contents of the 

 closed space. In the current number of Wiedemann' s Annalcii, 

 Herr Galitzini gives evidence to show that tc thus determined, 

 although it is independent of the amount of substance contained 

 in the closed space, is lower (it may be considerably lower) than 

 the true critical temperature, or the temperature at which liquid 

 ani saturated vapour have the same density. By very slow and 

 regular cooling he also finds that the peculiar misty appearances 

 which are usually held to be invariably associated with the 

 critical state are not observed. Amongst other conclusions, his 

 experiments, which it is to be noted were made on ether, lead 

 him to believe that at temperatures even considerably higher 

 than the critical temperature a substance at constant pressure 

 may have different densities, different in some cases to the 

 extent of 25 per cent. This last result the author attributes to 

 the presence of molecular complexes in the substance : if its 

 validity is established, it will of course overthrow the generally 

 accepted idea that at any temperature above the critical tempera- 

 ture for a given value of the pressure there is only one value 

 of the volume. 



Ax interesting paper on the various electric wave systems 

 obtained by Lecher's method has been communicated to the 

 R. Accademia della Scienza di Torino by Signor Mazotto. The 

 effect of varying the lengths of the primary and secondary wires, 

 and the distance apart of the plates of the condensers, has been 

 studied. As an indicator of the points of maximum difference 

 of potential along the wires, the author uses two short wires 

 partly coiled round india-rubber tubes, which slide along the 

 secondary wires, the ends of the wires being brought to within 

 about 2 cm. of each other. If, when the apparatus is working in 

 the dark, the fingers are brought near the platinum tips of these 

 wires, two small luminous stars appear at these tips when the 

 bridge over the secondary is in the vicinity of a node. When 

 at a node these sparks become very conspicuous, even without 

 the presence of the fingers. This indicator is said to have the 

 advantage over the Geissler tube used by Lecher, that it shows 

 more distinctly the maxima and minima, is less fatiguing to the 

 eyes, and less capricious in its action. The number of nodal 

 systems formed when, the primary system being kept consant, 

 the bridge on the secondary wires is moved to different parts, 

 were found to be more nu-xierous than Lecher's observations 

 NO. 1256, VOL. 49] 



would seem to indicate. The " harmonics " of the fundamental 

 system were not the only higher systems that were produced^ 

 it being found possible, by altering the position of the bridges 

 to produce any system intermediate between two harmonics 

 It was also found, when the second bridge was placed at a 

 fixed piint, that the nodal system •; obtained by moving the first 

 bridge were independent, in position and intensity, of the state 

 of the system beyond the second "^ridge. The wave-lengths 

 obtained experimentally were compared with those given by 

 the formula of Salvioni, and found to agree fairly well. The 

 curves obtained by the author, and a full account 6f his 

 method, has been published in the Electrician, vol. xxxii. p. 60. 



The following translation of a rq^Iy given by Prof Galileo 

 Ferraris to a young lady who asked what electricity was, is 

 given by the Electrician. Prof. Ferrari-; his conferred a great 

 benefit on all those who are supposed to have any knowledge 

 of that magic science electricity, and are therefore continually 

 being asked this question, though whether the reply satisfied the 

 questioner is rather doubtful. His reply was : — " Maxwell has 

 demonstrated that luminous vibrations can be nothing else than 

 periodic variations of electro-magnetic forces ; Hertz, in proving 

 by experimentsthat electro-magnetic oscillations are propagated 

 like light, has given an experimental basis to the theory of 

 Maxwell. This gave birth to the idea that the luminiferous 

 ether and the seat of electric and magnetic forces are one and 

 the same thing. This being established, I can now, my dear 

 young lady, reply to the question that you put to me : What is 

 electricity ? It is not only the formidable agent which now and 

 then shatters and tears the atmosphere, terrifying you with the 

 crash of its thunder, but it is also the life-giving agent which 

 sends from heaven to earth, with light and heat, the magic of 

 colours and the breath of life. It is that which makes your 

 heart beat to the palpitations of the outside world, it is that 

 which has the power to transmit to your soul the enchantment 

 of a look and the grace of a smile." 



The current Comptes yicv//?« contains an important correction 

 to the numbers given by M. Blondlo". for the velocity of an 

 electric disturbance in high conductivity copper ( Comptes Rendiis, 

 October 23). The values were expressed in kilometres per 

 second instead of thousands of kilometres per second, so each of 

 the velocities given in our issue of November 9 (p. 37) must 

 be increased by one thousand, in order to be correct. 



A VERY important paper, by Dr. Uschinsky, on the cultivation 

 of pathogenic bacteria in media, devoid of all albuminoids, 

 appears in the Archives de mcdecine cxperimentale, No. 3, 1893. 

 Pathogenic organisms thus grown do not lose their virulent 

 properties and, moreover, elaborate toxic substances, for on pass- 

 ing the media in which they have been cultivated through a 

 Chamberland filter, the filtrate was found to be toxic. In a 

 more recent paper, published in the Centralbla't filr B.ikteriolorie, 

 vol. xiv. No. 10, 1893, Dr. Uschinsky states that in order to 

 obtain more satisfactory growths of the bacteria in question, he 

 has introduced some modifica'rions into the composition of the 

 culture medium, which now affords as suitable a pabulum for 

 their cultivation as ordinary bouilbn. The following is the 

 composition of this non-albuminous medium : — Water, iodd ; 

 glycerine, 30-40; sodium chloride, 5-7 ; calcium chloride, o'l ; 

 magnesium sulphate, 0'2-o-4 ; dipotassium phosphate, 2-2-5 ; 

 ammonium lactate, 6-7 ; sodium aspartate, 3 '4. The organisms 

 of cholera, diphtheria, tetanus, typhoid and others have all been 

 grown successfully in the above. The poisonoas substances 

 elaborated by bacteria are, therefore, not necessarily due to 

 their decomposition of the albumen contained in the ordinary 

 culture media employed, but must rather be regarded as the 

 result of synthesis ; the materials produced, says Dr. 



