MICROSCOPE 



3792 



MIDAS 



lenses are farther apart or nearer together; thus 

 the observer may increase the magnifying 

 power of the instrument by extending the tube. 

 Most compound microscopes have three object 

 glasses and one eyepiece. A microscope hav- 



DIAGRAM SHOWING PATH OF LIGHT RAYS 



FI Upper focal plane of objective 



Fa Lower focal plane of eyepiece 



A Optical tube lengths distance between FI and 

 F 2 



Oi Object 



Oo Real image in F2, transposed by the collective 

 lens, to 



Os Real image in eyepiece diaphragm 



04 Virtual image formed at the projection dis- 

 tance C, 250 mm. from 



EP Eyepoint 



CD Condenser diaphragm 



L Mechanical tube length (160 mm.) 



1, 2, 3 Three pencils of parallel light corning from 

 different points of a distant illuminant, for 

 instance, a white cloud, which illuminate 

 three different points of the object 



ing two tubes to be used with both eyes is 

 called a binocular. For the various parts of a 

 compound microscope see the accompanying 

 illustration. The first instrument of this kind 

 was made in 1590 by a Hollander named Zacha- 

 rias Janssen; every generation has witnessed 

 important improvements. 



Most objects can be easily seen under the 

 microscope, but those which cannot need spe- 

 cial treatment and are placed upon a glass 

 mounting prepared for the purpose and covered 

 with a thin glass which is cemented in place 

 with Canada balsam. Specimens containing 

 disease germs and those in which minute cell 

 structures are to be shown must be spread on 

 glass, dried, passed through a blue flame and 

 stained with coal-tar or aniline dyes, as juch- 

 sine or methylene blue, or with gentian violet. 



Some Results of Microscopy. Many marvels 

 of insect and plant life and hidden secrets of 

 the mineral kingdom have been revealed to the 

 scientist by means of the microscope ; but more 

 than this, the perfection of the instrument has 

 revolutionized the science of medicine. A drop 

 of blood may now be examined and so magni- 

 fied that the physician can tell whether or not 

 it contains any of those minute forms of animal 

 life that mean disease. Bacteriology, the study 

 of bacteria, could not have been pursued if man 

 had never had a knowledge of the compound 

 microscope, and the various disease germs, 

 those that are responsible for malaria, typhoid 

 fever, diphtheria, etc., could not have been de- 

 tected. The microscope has, therefore, been a 

 wonderful agent in destroying the power of 

 disease and in making the world a more health- 

 ful place in which to live. C.R.M. 



Consult Clark's Practical Method in Micros- 

 copy; Carpenter's The Microscope. 



MIDAS, mi'dahs, a mythical king of Phrygia 

 who had a wondrous garden into which Silenus 

 loved to go. The king, by mixing some poison 

 in a fountain, succeeded in capturing the old 

 satyr, whom, after a ^ime, he returned to Bac- 

 chus. Pleased at regaining his old tutor, Bac- 

 chus conferred upon Midas the power of turn- 

 ing to gold everything he touched. When this 

 power proved a curse, by turning his food to 

 gold, the king besought release from Bacchus 

 and was told that if he bathed in the river 

 Pactolus he would be freed. 



Once Midas acted as judge between Apollo 

 and Pan in a musical contest, and decided in 

 favor of the latter. This so enraged Apollo 

 that he caused a pair of ass's ears to grow upon 

 the king's head. Midas tried to conceal the 

 deformity, but a slave discovered it when dress- 

 ing the ruler's hair. Afraid to tell, yet unable 

 to keep the strange secret, the slave dug a 

 hole in the earth and there whispered his funny 

 tale. Later, reeds grew up over the spot, and 

 whenever the wind blew over them they sang 

 to all passers-by, "King Midas has ass's ears." 



