514 HOMES WITHOUT HANDS. 



suspicions which would be aroused by a sheet of blank paper. 

 The almost colorless solution leaves no. mark, and the letter passes 

 without comment until it reaches the person who is in the secret. 

 He pours some decoction of galls into a wide and flat vessel, and 

 warily dips the letter into it, so as to "Vet it; or he saturates a 

 cloth with the decoction, and lays the letter upon it. The tannin 

 then acts upon the solution of iron, ink is formed by their com- 

 bination, and the formerly invisible words immediately become 

 plain and legible. 



A decoction of oak bark would make ink, though of inferior 

 quality, and so would tea, inasmuch as the tea-leaf contains a large 

 amount of tannin. In fact, whenever the ink in the bottle be- 

 comes thick, it can always be restored by adding to it a little 

 strong tea, which not only gives the requisite liquidity, but does 

 so without affecting the blackness, which would probably be the 

 case if simple water were added. 



The two principal ingredients of the ink which is in common 

 use are sulphate of iron' and the galls of a species of oak called 

 Quercus infectoria, which grows in large quantities in the Levant. 

 They are technically termed Aleppo galls, and are divided'into 

 several classes, according to their value. Besides these two in- 

 gredients a little gum is added, in order to give consistency, and 

 a very little corrosive sublimate or creosote, to prevent the growth 

 of mould. The proportione are generally six ounces of pounded 

 galls, four ounces of copperas, and four ounces of gum-arabic to 

 six pints of water. 



In the upper left-hand corner of the illustration two of these 

 galls are seen upon a branch of the oak. 



They are necessarily much reduced in size, their ordinary di- 

 mensions being about equal to those of Cynips Kollari. For the 

 purposes of trade they are divided into black, blue, green, and 

 white galls. The last-mentioned class of galls includes those from 

 which the insects have escaped, and which are consequently weak- 

 ened in astringency. They are so called because they assume a 

 paler hue than the three first classes, in which the insect still Re- 

 mains. In shape, the ink gall is nearly spherical, with a slight 

 tendency to a pear-like form, and their exterior is defended by a 

 few short, stout, and rather sharp prickles. 



I can not but think that the gall insect affords a proof that the 

 most insignificant objects of creation have their uses, provided 

 that we could only discover them. Nature is a vast treasure- 



