Irr] AND SYMBOLS. 183 



every word becoming visible and bright blue when the paper 

 was washed over with iodine ! This wonderful substance, 

 iodine, has the property of rendering starch blue or violet 

 colour ; and as rice contains a considerable quantity of starch, 

 an invisible ink prepared from it assumes that hue when 

 touched with iodine, though previously quite colourless. TH. 



The Perils of Irascibility. 



Some men are so irascible that they will quarrel at the slightest 

 thing. They are like the larvae of the Megacephalce (a group 

 allied to the tiger-beetles), which are described as being so rapa- 

 cious and irritable that they seize at anything that disturbs them. 

 In this way they are easily taken by inserting a straw in their 

 burrows, which they instantly seize with their mandibles and 

 pertinaciously retain. In this, their easy capture, they remind 

 us of the ready way in which the irascible men, already referred 

 to, are ensnared by those who, knowing their propensities, are 

 able, by the necessary provocation, to obtain facile conquests 

 over them. Such are the perils of irascibility. MU. 



Shocks of Irritable Temper. 



Electrical fish are those fish which have the remarkable pro- 

 perty of giving, when touched, shocks like those of the Leyden 

 jar. Of these fish there are several species, the best known of 

 which are the torpedo, the gymnotus, and the silurus. The tor- 

 pedo, which is very common in the Mediterranean, has been 

 carefully studied by MM. Becquerel and Breschet, in France, 

 and by M. Matteucci, in Italy. The gymnotus has been inves- 

 tigated by Humboldt and Bonpland in South America, and in 

 England by Faraday, who had the opportunity of examining 

 live specimens. The shock that they give serves both as a 

 means of offence and of defence. It is purely voluntary, and 

 becomes gradually weakened as it is repeated and as these 

 animals lose their vitality, for the electrical action soon exhausts 

 them materially. Amongst the " odd fish " of human society 

 are the constitutionally irritable ones. There are several varieties 

 of them, but they all resemble each other in that they are perpetu- 



