August io, 1893] 



NA TURE 



553 



fectant than was required when the organism was submitted to 

 it without any such preparation. Trambusti examined the 

 behaviour of various bacteria in the presence of corrosive sub- 

 limate, and found that they exhibited striking differences in 

 their ability to withstand this material. Thus whereas the 

 pneumococcus of Friedlander was trained to survive an addition 

 of I : 2000 parts of .the sublimate to the culture media, the 

 bacillus of fowl cholera was not able to withstand more than 

 I : 30,000. If, however, the pneumococcus were taken straight 

 from a fresh culture without any previous experience of the 

 disinfectant, it succumbed in a solution containing I : 15,000 

 parts. The bacillus of swine plague (Rouget des Pores) was 

 induced to resist an addition of I : 8000 parts, whereas without 

 training I : 15,000 parts infallibly destroyed it. As regards the 

 retention of their pathogenic properties amongst those organisms 

 investigated, the bacillus of swine plague was the only instance 

 in which the virulence was diminished during its treatment, an 

 addition of 1 : 20,000 parts of corrosive sublimate rendering it 

 innocuous, althoughits vitality was not destroyed in the presence 

 of I : 8000 parts. 



Messrs. E. and L. Mach have done a considerable 

 amount of work in connection with the photography of flying 

 bullets, air jets, and sound waves since their last publication on 

 this subject. Some results gleaned from a .series of about 1500 

 negatives have been recently communicated to the Vienna 

 Academy. Sharp images of Mannlicher rifle bullets were 

 obtained of 3 '5 cm. diameter. The disturbing electric contacts 

 in the field were dispensed with, as it was found possible to 

 close the spark circuit mechanically by means of the soundwave 

 produced by the bullet itself. A large number of experiments 

 were conducted with the interference refractometer invented 

 by Ludwig Mach, and constructed in a complete form with the 

 aid of the Academy. After some trials they succeeded in pro- 

 ducing homogeneous plane-parallel glass plates large enough to 

 obtain an interference field 8 cm. in diameter. If one part of 

 this field is occupied by a projectile, an air jet, or a sound wave 

 passing one of the interfering pencils, the interference bands, 

 usually rectilinear, appear bent in such a manner as to indicate 

 the change of density of air at any point. For the purpose of 

 instantaneous illumination the electric spark was usually 

 employed, but sometimes, especially in cases where a longer 

 illumination was admissible, as in the photography of air jets, 

 blue monochromatic sunlight was substituted. 



A SIMPLE instrument for trisecting any given angle, invented 

 by Dr. E. Eckhardt, is described in the Natiirwissenschaftliche 

 Wochenschrift . A straight rule has a slot running along two- 

 thirds of its length, with a pin capable of moving along it. A 

 bar is attached to this pin, and another bar to a rivet at the 

 inner end of the slot. Both these bars are equal in length to 

 the remaining third of the rule, and their free ends are joined 

 by means of another pin. When it is desired to trisect an 

 angle, the pin moving in the slot is placed at the vertex, and [ 

 the other pin in one of the sides, a parallel to the other side, ' 

 being drawn through the point occupied by the pin. A curve 

 is now drawn by means of a pencil attached to the unslolted 

 end of the bar, and the intersection of this curve and the 

 parallel referred to is the point of trisection required. The 

 instrument also gives an easy construction for an angle of 36° 

 1 and for the performance of the "golden section." It is ex- 

 I hibited at Chicago by " The Prussian Universities." 



At a recent meeting of the Socieie Francjaise de Physique, 

 j M. E. Ducretet described a method he had employed for 

 \ making high resistances without self-induction, and hence 

 j suitable for use with a telephone in Kolilrausch's method of 

 j measuring resistances. He uses a zigzag formed on platinised 

 glass very like that, composed of fine platinum wire, used by M. 



NO. I24I, VOL 48] 



Mergier, and finds that a piece of platinised glass 75 mm. by 

 no mm., allows of the construction of resistances varying from 

 25 to 100,000 ohms. The glass plates are fixed in a glass vessel 

 by means of an insulating cover, and this vessel is filled with 

 purified petroleum, which M. Pellat has shown to be a very good 

 insulator. In this manner all effects due to moisture in the air 

 are removed, while it is easy to measure the temperature. A 

 layer of mercury, of variable thickness, at the bottom of the 

 vessel allows of the resistance being adjusted to any desired 

 value. 



While engaged on some measurements on the electrical 

 resistance of the human body M. Mergier was led to the con- 

 struction of a simple instrument which, while being easily 

 manipulated, should be capable of making such a measurement 

 with accuracy. The instrument consists of two coils of insu- 

 lated wire, fixed with their planes at right angles to each other, 

 and placed within the field of a strong horse-shoe magnet. 

 These two coils are connected in series with the resistances to 

 be compared, and to the terminals of a battery. Under these 

 circumstances, the position of equilibrium of the coils de- 

 pends only on the ratio of the resistances of the two branches 

 (coil and added resistance), and is independent of the value of 

 the electromotive force of the battery. The current is led into 

 the coils by three metallic points, placed one vertically above 

 the other, and dipping into mercury cups. The coils are sus- 

 pended by a silk fibre or from a steel point working in an agate 

 cup. For use with alternating currents the magnet is replaced 

 by two fixed coils, which are also connected to the circuits con- 

 taining the resistances to be compared. 



Messrs. Deighton, Bell and Co. have published a second 

 edition of Dr. W. H. Besant's excellent " Treatise on Dyna- 

 mics." 



Messrs. J and A. Churchill have issued a little volume 

 entitled " Homburg-Spa : an Introduction to its Waters and 

 their Use," by Dr. Arnold Schetelig. 



We have received a report containing the results of observa- 

 tions made at Magdeburg meteorological observatory during 

 1891, under the direction of Ilerr A. W. Griitzmacher. 



Dr. R. W. Shufeldt, in The Auk of July, gives an account 

 of an examination of the trunk skeleton of a hybrid grouse. His 

 observations confirm an opinion expressed some years ago, that 

 of all the North American grouse, the genera Pediocaeles and 

 Tyvipanuchus are most nearly related to each other ; in fact, so 

 close is the relation, that the species are fertile inter se. 



Bulletin 42 of the Purdue University Agricultural Experi- 

 ment Station contains a paper by Mr. J. C. Arthur on the 

 relation of the number of eyes on the seed tuber of the potato to 

 the crop obtained. The experimental data brought forward 

 indicate that the proper way to cut potatoes for planting is to 

 divide them into pieces of suitable size, without regard to the 

 distribution of the eyes. In other words, the number of eyes 

 per piece is immaterial, so that the weight or size of the piece 

 should be the all-important factor in preparing seed material. 



The annual report of the Royal Botanic Garden, Calcutta, of 

 which Lieut.-Col. G. King, F.R.S., is superintendent, has 

 been issued. From it we learn that all the efforts to introduce 

 the cultivation of the Japanese paper mulberry have failed. As 

 the superintendent points out, this mulberry yields a beautiful 

 fibre, which is naturally so white that it requires very little 

 bleaching, hence it seems a pity that no wealthy landowner has 

 taken up its cultivation on a large scale. 



The administration report of the Central Museum for 1892-93 

 has been prepared by Dr. II. Warth, officiating superintendent, 



