M I D G E M I N E R A LO G Y. 



own transformation produces only a few threads which 

 fasten the tail and girt the middle of the chrysalis, 

 should become provided with the superabundant sup- 

 ply in consequence of its interior being nearly de- 

 voured. In the case of those species indeed which 

 infest the tribes of Bombyccs and Arctwe, it appears 

 that the imperfect cocoon spun by the caterpillar 

 mav serve for the envelope of its parasites. In gene- 

 ral they are found in lepidopterous larvae, but Mr. 

 Curtis has obtained one species out of that of an 

 aphidivorous fly." 



In the eighth number of the Entomological Maga- 

 zine, Mr. Haiiday has given a monograph of the 

 genus, describing fifty species, and indicating more 

 than tweniy others described by previous authors. 

 They are ail of minute size, not exceeding one eighth 

 of an inch in length. 



MIDGE. The ordinary English name given to 

 numerous minute species of Ttpididce, having the ap- 

 pearance and being of the size of the common gnat, 

 but wanting the elongated proboscis of that insect. 

 They chiefly belong to the genera Chironomus, Corethra, 

 and Tanypus, and are often miscalled gnats, which 

 name ought to be restricted to the familv Culicida;. 



M I G N O N ETTE. Is the Reseda odorata of Lin- 

 naeus, a well-known flower-garden plant. 



MILFOIL. Is the Achillca anglica of G. Don, 

 a common plant in every pasture, belonging to Com- 

 positce. 



MIL I OLA (Lamarck). A minute shell which 

 has been found on Fuci in the island of Cors5ca.it is 

 also frequently met with in a fossil state. It belongs 

 to the familv Spherulacea. 



MILIUM (Linnaeus). A genus of grass, chiefly 

 annuals, found in different parts of Europe. The 

 M. effuKum is the millet-grass of English botany. 



MILK WORT. Is the PolygalaviilgarisofTomne- 

 fort, a common plant found in dry pastures. 



MILLERIA (Linnaeus). A genus of tropical 

 annuals, named in honour of " the prince of gar- 

 deners," Philip Miller, F.R.S., many years curator of 

 the Chelsea botanic garden. In our collections they 

 are treated as tender annuals , i. e. sown in a hot- 

 bed or hot-house, and planted out in the borders 

 before Midsummer, where they ripen seeds. They 

 belong to the order Composite. 



MIMETES(Dr. R. Brown). A genus of ever- 

 green shrubs from the Cape of Good Hope, belonging 

 to the Proteaceac, and nearly allied to the type of 

 that order. These plants do not thrive well with much 

 moisture, and therefore require to be grown in well- 

 drained pots and in light sandy loam. They may be 

 propagated by cuttings if kept free from damp. 



MIMOSA (Linnaeus). A genus of plants so called, 

 because some of them imitate the action of animals by 

 shrinking from the touch of other bodies. The Mi- 

 mosas are distinguished from Acacice by their jointed 

 pods and sensitive properties. They grow well in the 

 green-house mixture of loam and moor-earth, and may 

 be propagated by cuttings, but much more con- 

 veniently by seeds. They belong to the natural 

 order Lepuniinosce, 



MIMULUS (Linnaeus). A genus of very inter- 

 esting annual and perennial herbs, natives of Ame- 

 rica. The flowers are didynamous, and the genus 

 belongs to the natural order Scroplndarince. They 

 grow in any rich soil, and are readily increased from 

 eeds which ripen abundantly. There are many new 



varieties of the Chilian species. 



1 



MINERALOGY. Our earth has sometimes been, 

 defined as a " huge mineral," but the discoveries in 

 modern chemistry show that it is composed of a vast 

 number of compound bodies continually acted upon, 

 by changes of temperature, and the solvent character 

 of the fluids which percolate through the interstices 

 which it contains. The characters of these bodies 

 differ most materially both in their external appear- 

 ance and in their effects on the human frame. Thus 

 we find in the same neighbourhood poisons of the 

 most deadly character assuming forms of the most 

 exquisite symmetry, whilst metals which are of the 

 greatest service in domestic economy and the useful 

 arts are apparently worthless if not repulsive in their 

 appearance. 



The iron that forms the warrior's weapon as well 

 as the more useful implements of the agriculturist, 

 can only be procured with advantage by an acquaint- 

 ance with the mineral bodies with which our earth is 

 so thickly studded ; and the steam engine, that mighty 

 abridger of time and space, owes much of its utility, 

 to this country having given a peculiar degree of 

 attention to practical mineralogy. The great im- 

 portance of the mineral kingdom in a scientific point 

 of view is in no shape confined to the natural history 

 characteristics of mineral bodies ; and though the 

 properties which some minerals possess of phospho- 

 rescence, electricity, and magnetism, may only serve 

 to excite the attention of the curious, yet the ablest 

 mathematician may find ample employment in the 

 more abstruse problems of crystalisation and polarised 

 light. This is, at the same time, the science which 

 includes within its ample range the marbles of the 

 statuary and the architect, the metals of the manu- 

 facturer, the gems of the jeweller, and the soils of the 

 agriculturist. It can never, therefore, be deemed 

 uninteresting or unimportant. Nothing can be more 

 beautiful than the caverns to be met with in primitive 

 rocks, whose walls are lined with pure and various 

 coloured crystallised topaz, beryl, and rock crystal ; 

 and the gneiss, granite, and mica slate, with imbedded, 

 grains and crystals of sapphire, chrysoberyl, garnet,, 

 emerald, and ruby, seem to realise the oriental tales 

 of diamond valleys and emerald caves. But it is not 

 the beauties of the gems alone that attract our atten- 

 tion ; the varying composition of the mighty masses 

 which compose the crust of the earth' surface, and 

 their conversion into soils no less than the operations 

 at once mighty and minute which turn the hard and 

 sterile rock into soft, and fertile earth, are well worthy 

 of our attention. Some idea may be formed of the 

 method in which this is performed by referring to the 

 instance of porcelain granite. " This substance," says 

 Sir Humphry Davy, "consists of three ingredients 

 quartz, feldspar, and mica. The quartz is almost 

 pure siliceous earth, in a crystalline form. The feld- 

 spar and mica are compounded substances ; both 

 contain silica, alumina, and oxide of iron ; in the 

 feldspar there are usually lime and potassa ; in the 

 mica, lime and magnesia. When a granite rock of 

 this kind has been long exposed to the influence of 

 air and water, the lime and the potassa contained in 

 its constituent parts are acted upon by water or car- 

 bonic acid, and the oxide of iron, which is almost 

 always in its least oxidised state, tends to combiNe 

 with more oxygen ; the consequence is that the feld- 

 spar decomposes, and likewise the mica, but the first 

 the most rapidly. The feldspar, which is as it werq 

 the cement of the stone, forms a fine clay ; the mica, 



