THE METRIC SYSTEM. 



lO CENTIMETERS DIVIDED INTO IOO MILLIMETERS. 



5 Centimeters. 5 Centimeters divided into 



3 % Centimeters. 



UNITS. The most commonly used divisions and multiples. 



THE METER FOR 

 LENGTH. . . . 



(Centimeter (cm.), l-iooths Meter; Millimeter (m.m.), i-ioooths Meter; Micron 



(/<), i-ioooths millimeter; the Micron is the unit in Micrometry (§ 157). 

 (Kilometer, 1000 Meters; used in measuring roads and other long distances. 

 the gram for ( Milligram (m.g.), i-ioooths gram. 



weight. . . . \ Kilogram, 1000 grams, used for ordinary masses, like groceries, etc. 

 the liter for ( Cubic Centimeter (cc), i-ioooths Liter. This is more common than the cor- 

 capacity. . . I rect form, Milliliter. 



Dimsions of the Units are indicated by the Latin prefixes: deci, i-ioth ; centi, i-iooth; Milli, 

 i-ioooth. 



Multiples are designated by Greek prefixes: deka, 10 times ; hecto, 100 times ; kilo, 1000 times ; 

 myria, 10,000 times. 



TABLE OF METRIC AND ENGLISH MEASURES. 



METER = ioo centimeters, 1000 millimeters, 1,000,000 microns, 39 3704 inches. 



Millimeter (mm.) = 1000 microns, y B tli millimeter, To L ff th meter, ^th inch, ap- 

 proximately. 



Micron (//) (Unit of Measure in Micrometry) = yjooth mm. xoo^ooo 1 ' 1 nieter. 

 (0.000039 inch) jjjoo 1 ' 1 inch, approximately. 



Inch (in.) = 25.399772 mm. (25 4 mm., approx. ) 



Liter — 1000 milliliters or 1 coo cubic centimeters, 1 quart (approx.) 



Cubic centimeter (cc. or cctm. ) = yoVo 1 " OI a liter. 



Fluid ounce (S Fluidrachms) = 29 578 cc. (30 cc, approx.) 



Gram =15 432 grains. 



Kilogram (kilo) = 2.204 avoirdupois pounds (2ith pounds, approx.) 



Ounce Avoirdupois = (437,1 grains) = 28.349 grams. \ , aoorox 1 



Ounce Troy or Apothecaries = (4S0 grains) =31. 103 grams, j ^ 6 ' ^V 



TEMPERATURE. 



To change Centigrade to Farenheit : ( C. X f ) + 32 = F. For example, to find 

 the equivalent of io° Centigrade, C. = io° (io° X f) -f 32 = 50 F. 



To change Farenheit to Centigrade: ( F. — 32°)Xf = C. For example, to re- 

 duce 50 Farenheit to Centigrade, F. =50°, and (50 — 32 ) Xf = io° C. ; or — 40 

 Farenheit to Centigrade, F. = — 40 ( — 40 — 32 ) = — 72 , whence — 72 X | 

 = - 40 C. 



Address of American Opticians : For the price of Microscopes and Microscopical supplies, the 

 student is advised to obtain a catalog of one or more of the opticians named below For the cat- 

 log of foreign opticians, see addresses in the table of tube-length, p. 15. Nearly all import for- 

 eign goods. 



The Bausch & Lomb Optical Co., New York City and Rochester, N. Y. 



Eimer and Amend, 205-211 Third Avenue, New York City 



The Franklin Educational Co., Harcourt St., Boston, Mass. 



L Grunow; 70 West -(9th St., New York 



TheGundlach Optical Co Rochester, N Y. 



Wm. Krafft, (representative of Leitz in America), 411 West 59th St., New York 



The Mcintosh Battery and Optical Co 521-531 Wabash Ave., Chicago, 111. 



Queen & Co.. Incorporated 1010 Chestnut St., Philadelphia, Pa. 



Richards & Co., Limited, 30 E. 18th St., New York, 108 Lake St,, Chicago, 111. 



Edward Pennock, 3609 Woodland Ave., Philadelphia, Pa. 



Spencer Lens Co 546 Main St., Buffalo, N. Y. 



Walmsley, Fuller & Co T i34-i36\Vabash Ave., Chicago, 111. 



Williams, Brown & Earle, 10th & Chestnut Sts., Philadelphia, Pa. 



G. S. Woolman, (Queen & Co., in New York), 116 Fulton St., New York 



J. Zentmayer, ■ • • 209 South nth St., Philadelphia, Pa, 



