100 VIEWS OF THE MICROSCOPIC WOKLU. 



preceding monsoon-storms have been most heavy, and the thunder and lightning 

 that attend them unusually frequent. The earth from which the nitre has been 

 extracted, in a year or two becomes impregnated again, and the tendency of the 

 soil to reproduce it causes much trouble and annoyance to the occupants of 

 houses. Bishop Heber remarks "that the nitre can scarcely be prevented from 

 encroaching, in a few years, on the walls and floors of all lower rooms, so as to 

 render them unwholesome, and eventually uninhabitable." To such an extent 

 does it prevail at Tirhoot, that it may be brushed from off the lime walls of the 

 houses, and other humid places, almost in basketfuls, every two or three days. 



FLOWERS OF BENZOIN. A species of gum, known by the name of Benzoin^ 

 is extracted from a tree which grows in Java, and some other parts of the East. 

 An incision is made into its trunk and branches, and a fluid exudes from them, 

 which hardens upon exposure to the air, concreting into brittle masses. It 

 melts when subjected to a moderate heat, and sends forth a thick, white smoke, 

 which condenses, upon the underside of the cover of the vessel containing the 

 melted gum, in slender and delicate crystals of benzoic acid. These are beauti- 

 fully white and transparent, and emit a fragrant odor. A drop of the solution 

 of this acid exhibits very elegant crystallizations under the microscope. Sharp 

 crystals are first perceived forming at the edges, transparent, and without color, 

 which soon push forward towards the centre of the drop, in the form of running 

 vines and beautiful tufts of mimic foliage. Several specimens are delineated in 

 drawing 152, possessing the same characteristic form, but still differing in some 

 particulars. All consist of similar minute crystals gracefully clustered together ; 

 but while one shoots along in light and airy tracery, as in the right hand figure, 

 another, like that upon the left, extends laterally, and spreads its glittering- 

 branches from side to side; and in different parts of the field of view other 

 configurations start forth, and rich tuft-like figures are seen like the central 

 forms of the group. The largest tufts and vines appear dark to the eye from 

 the immense number of minute crystals which are there clustered together ; but 

 amid these, under a subdued light, wreaths of exquisitely delicate foliage are 

 seen, formed of the purest crystals, and gleaming like silver sprays. Inter- 

 spersed with the rest, crystallizations in the form of crosses occur, as shown in 

 the drawing. When the acid is dissolved in alcohol, and the solution spread upon 

 the glass, the crystallization proceeds with great swiftness, on account of the 

 rapid evaporation of the spirit. At one moment the eye of the observer gazes 

 upon nothing but a film of liquid, and at the next, on a sudden, at a single 

 flash, order springs forth, and the chaotic surface is profusely studded with all the 

 exquisite and graceful combinations which have been detailed. The delineations 

 in the figure are drawn from actual crystallizations, like all the rest, and repre- 

 sent forms of average dimensions. Some idea may be gained of the srnallnesa 

 of the crystals, from the fact, that the breadth of the group a, 6, is only tho 

 one-six-hundred and twentieth part of an inch. 



