304 



MICROCOSM MIDDLE AGES. 



the object is increased ten times ; but as its breadth 

 is also increased ten times, the real magnifying 

 power of the lens is ten times ten, or a hundred. The 

 common form of the magnifiers employed for micro- 

 scopes is double-convex, and they should be made as 

 thin as possible ; for the wandering and spreading 

 out of the rays proceeding from an object when re- 

 fracted by the lens with spherical surfaces, whereby 

 an indistinctness is produced in its image, will be 

 decreased, as the square of the thickness of the lens 

 employed, and the loss of light in passing through 

 the lens is less in proportion as it is thin. Within a 

 few years diamonds have been formed into lenses in 

 consequence of their high refractive power, whereby 

 we can obtain lenses of any degree of magnifying 

 power with comparatively shallow curves, and as the 

 dispersion of colour in this substance is as low as in 

 water, the lens is nearly achromatic. Next to the 

 diamond the sapphire possesses all the powers requi- 

 site for the formation of perfect magnifiers, and pre- 

 sents less difficulty in their construction ; hence the 

 expense of employing it is considerably less. 



M. M. Trecourt and Oberhausen lately presented 

 to the Academy of Sciences at Paris, microscopic 

 lenses formed of diamond, sapphire, and ruby, all 

 ground to the same curvature. The diamond lens 

 magnifies 210 times, and with a compound eyeglass, 

 the power is extended to 245 ; the power of the sap- 

 phire, with the same eye-piece, is 255 ; and that of 

 the ruby 235. The grinding and polishing of these 

 lenses is very laborious. The polishing of the dia- 

 mond occupied twenty-four hours, the wheel making 

 not less than 200 revolutions per second. 



A compound refracting microscope is an instrument 

 consisting of two or more convex lenses, by one of 

 which an enlarged image of the object is formed, and 

 then by means of the other employed as an eyeglass, 

 a magnified representation of the enlarged image is 

 obtained. The distance at which the two lenses of 

 a compound microscope are placed from each other 

 must always exceed the sum of their focal lengths, 

 in order that the image may be formed by the object- 

 glass in the interior focus of the eyeglass. Com- 

 pound microscopes have been constructed of almost 

 all possible dimensions, from a few inches in length 

 to that of twenty feet ; but from experience it ap- 

 pears that whenever their magnitude is augmented 

 beyond a certain point, the effect is diminished, 

 though we suppose the amplifying power of both 

 microscopes the same. 



The solar microscope consists of a common micro- 

 scope connected with a reflector and condenser, the 

 former being used to throw the sun's light on the 

 latter, by which it is condensed to illuminate the ob- 

 ject placed in its focus. This object is also in the 

 focus of the microscopic lens on the other side of it, 

 which transmits a magnified image of it to a wall or 

 screen (sometimes a combination of two magnifying 

 lenses is used). The magnifying power will be greater 

 in proportion as the focal distance of the object-glass, 

 compared with the distance of the wall or screen from 

 the object-glass is less. The principle of the luccrnal 

 microscope is the same, except that a lamp is used 

 instead of the sun to illuminate the object ; this lamp 

 is enclosed in a lantern, to screen the light from the 

 observers. 



MICROCOSM (from /*<;;, little, and xoirpos, the 

 universe); the name given to man in the times when 

 astrology flourished, as it was supposed that his 

 organization accurately corresponded to the organiz- 

 ation of the universe, called in this case macrocosmos 

 (from (utKaof, meaning great, and xarftes, the uni- 

 verse). The different parts and limbs of man were 

 made to correspond to the different parts of the 

 universe ; and engravings are found in works of 



that time, in which man stands in the centre of the 

 universe, surrounded by lines indicating the various 

 connexions of the heavenly bodies with his limbs. 

 This idea owes its origin partly to the importance 

 which early ages attributed to the position of man 

 in the universe. The earth is at first always con- 

 ceived of as tlie centre of the universe ; the heavens 

 are a mere dome over the earth, to give light, &c.; 

 and man, the present lord of the earthly creation, is 

 considered actually the lord of all the creation. Close 

 relations between him and the vast cosmological 

 phenomena are then imagined. But the progress of 

 science makes man modest. It shows him that 

 he belongs only to one period of a small planet. 

 Microcosm is still used in a figurative sense for man. 



MICROSCOPICAL ANIMALS, or ANIMAL- 

 CULES. See Animalcula. 



MIDAS, the son of Gordius and Cybele, was an 

 ancient king of Phrygia, of whom many fables are 

 related. His story has the naivete of a nursery tale. 

 While he was yet in the cradle, the ants put corn in 

 his mouth, and the soothsayers prophesied that he 

 would acquire great riches. When he was king, and 

 Bacchus was travelling through Phrygia, Silenus lost 

 his way, and strayed to the court of the king. Midas 

 hospitably entertained him, and conducted him back 

 to Bacchus, who permitted Midas to choose what- 

 ever recompense he pleased. Midas requested that 

 every thing he touched might become gold, and the 

 god granted his wish. But when even his food was 

 transformed into gold at his touch, he implored Bac- 

 chus to take back the fatal privilege. The god then 

 commanded him to go up the river Pactolus, and to 

 dip his head in the sources of the stream, and after- 

 words to bathe in it. The property of transforming 

 every thing into gold was then transferred to the 

 waters of the Pactolus. Pan and Apollo appointed 

 Midas and Timolus their umpires in a musical con- 

 test. Midas gave to the syrinx of Pan the prefer- 

 ence over the lyre of Apollo, and was therefore pun- 

 ished by the latter with a pair of ass's ears. Hence 

 the phrase ears of Midas, often bestowed upon ignor- 

 ant critics. Midas now exerted himself to conceal 

 this ornament of his head by his royal cap ; but he 

 was obliged to uncover his head under the hands of 

 his hair-dresser ; and, although the king ordered 

 secrecy under the severest penalty, yet the secret 

 weighed upon the barber so heavily that, to unbur- 

 den his mind, he dug a hole in the ground, and whis- 

 pered in it, " king Midas has ass's ears,'' and then 

 covered up the hole. Soon after weeds sprang up 

 on this spot, which, when moved by the wind, mur- 

 mured the words of the barber. Thus the secret 

 was divulged. 



MIDDLE AGES ; that period in the history of 

 Europe, which begins with the final destruction of 

 the Roman empire, and, by some historians, is consid- 

 ered to end with the reformation ; by others, with 

 the discovery of America ; by others, with the con- 

 quest of Constantinople ; and again, by some, with 

 the invention of the art of printing ; all of which 

 may be right, according to the special purpose of 

 the historian. In general, it may be said, the middle 

 ages embrace that period of history in which the 

 feudal system was established and developed, down 

 to the most prominent events which necessarily led 

 to its overthrow, though its consequences and influ- 

 ence are still very observable in the states of Europe. 

 (See Feudal System, and Chivalry.") The first cen- 

 turies of the middle ages are often termed the dark 

 ages a name which they certainly deserve. Still, 

 however, the destruction of the Roman institutions, 

 by. the irruption of barbarous tribes, is often unduly 

 lamented, and the beneficial consequences attending 

 it overlooked. True it is, that many of the acquisi- 









