Progress of Invention. 153 



a mixture of common tin solder and an amalgam of zinc and mer- 

 cury. The proportions may vary from equal weights of tin solder 

 and amalgam to one part amalgam and three parts tin solder. 



Preservation of Liquors containing Alcohol. — Liquors, such as 

 beer, containing comparatively small quantities of alcohol, have a 

 great tendency to natural fermentation. It has been found that 

 this tendency may be lessened, and even destroyed, by a judicious 

 application of heat. The higher the temperature, the more effec- 

 tive it is ; but unless kept within certain limits, the flavour will be 

 deteriorated, or even destroyed — a disagreeable one supervening. 

 It is enough if a temperature at all higher than 45° Cent, is 

 reached ; but that between 28 J and 58 D must be allowed to continue 

 for as short a time as possible, since the various temperatures 

 between these points are exactly those most favourable to the 

 development of natural fermentation. The temperature should be 

 raised as rapidly as possible to between 48° and 58% which should 

 be maintained for at least twenty, and at most sixty, minutes ; after 

 which the cooling should be rapid, and the liquor should then be 

 transmitted to barrels which have been previously filled with car- 

 bonic acid. 



New Application op Electricity. — It is necessary that the 

 person attending on a power-loom should carefully watch and 

 remedy the breaking of a thread ; and as several looms may be in 

 charge of one attendant, it would be very useful that his attention 

 should be directed to a broken thread. This is now done with 

 great simplicity and certainty in the case of the stocking-machine, 

 by means of electricity ; and there is no reason why the same con- 

 trivance should not be applicable in other cases. A small lever 

 rests on the thread, and retains its position as long as the thread is 

 whole. But the instant the thread breaks, the lever falls, and com- 

 pletes connection between the poles of a galvanic battery, which 

 excites a small electro-magnet, and sets a bell-ringing apparatus in 

 action. This attracts the notice of the attendant, so that the broken 

 thread is instantly made whole again. 



The Latent Image. — The photographer had long been sur- 

 prised at, but unable to explain, the existence of the latent image ; 

 and its development has never failed to astonish the uninitiated — 

 its a]3pearance being something resembling the effects of magic. 

 Its nature, thanks to Mr. Carey Lea, is no longer a mystery ; and 

 its existence is shown to be due to well-known optical principles. 

 There are certain substances which, in contact with organic matters 

 (thus, iodide of silver), undergo a marked chemical change when 

 exposed to the action of light. It was considered that the presence 

 of the luminous body itself was required to produce this effect, 

 which is not, however, the case. It has long been known that 

 certain substances are capable of absorbing light and again emitting 

 it — some in a few seconds, some during a much longer period. It 

 is true that this fact was remarked only regarding the luminous 

 rays ; but we might infer it from analogy with regard to the actinic 

 rays also ; and there is no question of it regarding the calorific. It 

 explains, indeed, the fact, that an engraving exposed for a few 



