]M. 



• KNOWLEDGE • 



[Fbr 23, 1883. 



Tlie instrument may also be connected, as shown by 

 Fig. 2, wlierc the two discs, DD, form the ends of sound 

 boxes, SS, having flexible tubes leading from them to 

 funnel mouths, EE, that can be held to both ears. The 



wire, W, may also include in its circuit the primary coil of 

 an induction coil, I, the other wire, X, including in its cir- 

 cuit the secondary coil of I. The gain effected by using 

 the induction coil is to increase the effect upon the local 

 battery current. 



Fig. 3. 



Fig. 3 shows a convenient form in which the instrument 

 may be made. The iron wire. A, is, in this instance, 

 enclosed in a wooden casing, C, to which one end of the 

 wire may, or may not, be attached, the other end being 

 attached to the single disc, D, which is clamped to the 

 casing by an ear-piece, M. This form is very light, its 

 total weight being no more than four ounces. 



As regards the efficiency of the instrument, we may say 

 that it reproduces the sounds with remarkable clearness, 

 even in this, its crudest form ; and when the transmitter 

 (which we are not yet at liberty to describe), as well as a 

 further improved form of receiver, are placed before the 

 public, we imagine that th<' result will fully endorse our 

 sanguine anticipations. 



It is as well, perhaps, to mention that the inventors of 

 the receiver we ha\e descrilied make no general claim to 

 the use of an iron or steel wire coiled with a conducting 

 wire for producing sounds under tlie influence of electric 

 currents, but claim : — 



" The construction of a telephonic receiving instrument 



consisting of a magnetic wire attached to a sonorous disc 

 or plate, and wound with a primary coil connected to a 

 local liattery, and with a secondary coil connect*''! to the 

 telephonic line wire, as described." 



PLEASANT HOURS WITH THE 

 MICROSCOPE. 



By Henry J. Slack, F.G.S., F.R.M.S. 



A SACCHARINE fluid, intended for alcoholic fermenta- 

 tion, is liaVile, as brewers know to their cost, to turn 

 sour, if, in addition to yeast ferments, there are also ^•inegar 

 ferments present. IMinute organisms, or germs of such, 

 capalile of acting upon alcohol and producing vinegar, are 

 so widely diffused that it is only necessary to expose a 

 suitable fluid to the air of ordinary places to be sure of 

 their appearance in the course of time. A mere mixture 

 of alcohol and water does not suffice for the growth of these 

 organisms; but the addition of a little gluten, or some such 

 substance, allows them to develop. xV mixture of one part 

 of sugar, six of water, one of brandy, or other strong 

 alcoholic liquor, with a little yeast, put into a cask with 

 the bung-hole open, and kept at a temperature of 70° or 80°, 

 turns to vinegar in a month or six weeks, and a micro- 

 scopic examination will show that besides yeast cells, others 

 of a different character are present. The vinegar ferment 

 grows much faster when a warm malt liquor is allowed to 

 trickle over birch twigs, or shavings freely exposed to air. 

 This is a well-known mode of vinegar making, and the 

 twigs are soon covered with a coating of the ferment plants. 

 When these ferments form a loose gelatinous deposit, it is 

 called the " mother of vinegar ; " but they may be obtained 

 in another condition, called the vinegar plant, which is a 

 very useful article in domestic economy. 



As an instance of its formation, a case may be mentioned 

 of a cask of apple- wine (apple-juice and sugar), which showed 

 signs of sourness, and was therefore destined for vinegar. 

 Several gallons were put into a large brown pan with some 

 yeast, and loosely covered with a cloth, to keep out dust. 

 It was left in a dark and rather cool cellar, below the tem- 

 perature at which the acetification would proceed rapidly. 

 In a few months there appeared floating on the liquid a 

 dense, tough mass, like wet, buff leather, or a big slice of 

 tripe, and the whole quantity of the fluid proved to be 

 good vinegar, rather above the usual strength. 



A vinegar plant is not a very easy thing to examine 

 microscopically, which may account for its being 

 erroneously described in some books. A modest power 

 (100 to 1.50 x) applied to a thin strip, shows groups of 

 cells more or less resembling common yeast cells, and 

 usually some sausage-shaped cells, with small cells inside 

 them. The main mass is, not as has been said, a 

 " structureless jelly," but densely crowded with small 

 beaded cells, which gi^e it a sort of wrinkled aspect under 

 the magnification mentioned. To see more, a very small 

 piece should be stretched and squeezed out, first with an 

 old penknife — which the acid soon blunts — then by 

 pressing on a slide with a thin covering glass. When 

 partially dried and reduced to a film, a ^th objective, or 

 higher power if at hand, and careful illumination, shows 

 that a minute portion must contain millions of extremely 

 small beaded cells of the bacterium character. They appear 

 most plainly when the objective is reduced by a stop to a 

 moderate angle and the film is illuminated with Mr. 

 Wenham's peculiar dark ground arrangement for high 

 powers. This apparatus throws a beam of light at such 

 an angle that it is totally reflected by tlie glass slide, 



