7. It is 6 hr. 52 min. 40 sec. A.M. in Harrisburg, Ans. 91° 37′ 30′′. what is its longi Penn., when it is noon at Greenwich; tude? Ans. 76° 50'. 8. When it is 8 o'clock A.M. in New Orleans, it is 9 hr. 5 min. 11 sec. in Albany; what is the difference of longitude? Ans. 16° 17′ 45′′. TEMPERATURE. 183. A Thermometer is an instrument for meas uring variations of heat and temperature. There are three methods of registering heat and temperature by means of thermometers. Fahrenheit's, used in the United States, England, and Holland; Réaumer's, used in Russia, Spain, and Turkey; and Celsius's, called the Centigrade, used in France, Germany, Sweden, and some other countries of Europe. In Fahrenheit's (F.) the freezing point is marked 32°, and the boiling point 212°. In Réaumer's (R.) the freezing point is zero, and the boiling point 80°. The Centigrade (C.) has the freezing point zero, and the boiling point 100°. 184. To reduce from one scale to another. RULE I.-To express degrees Fahrenheit in Réaumer, deduct 32 and take of the remainder; conversely, to change Réaumer to Fahrenheit, multiply by and add 32 to the product. Formulas: R. = † (F. — 32°). F. R. + 32°. ILLUSTRATIONS. = 1. Express 59° F. in Réaumer's scale. 3. Express in Réaumer, 68° F.; 95° F.; 77° F.; 140° F. Ans. 16° R.; 28° R.; 20° R.; 48° R. 4. Express in Fahrenheit, 32° R.; 76° R.; 8° R.; 50° R. Ans. 104° F.; 203° F.; 50° F.; 1441° F. 5. Express 47° F. in R.; 59° R. in F.; 67° R. in F.; 14° F. in R.; 10° R. in F. Ans. 6° R.; 164° F.; 1823° F.; -8° R.; 541° F. 6. Express 5° F. in R.; 4° R. in F.: 252° R. in F. Ans. 12° R.; 23° F.; 599° F. RULE II. To express degrees Fahrenheit in Centigrade, subtract 32 and take of the remainder; conversely, to change Centigrade to Fahrenheit, multiply by and add 32 to the product. Formulas: C. — § (F. — 32°). F. = C. + 32°. 3. Express in Centigrade, 95° F.; 131° F.; 41° F.; 203° F. Ans. 35° C.; 55° C.; 5° C.; 95° C. 4. Express in Fahrenheit, 15° C.; 90° C.; 130° C.; 30° C. Ans. 59° F.; 194° F.; 266° F.; 86° F. 5. Express in C. 14° F. In C. 71° F. In F. 18° C. In F. 91° C. Ans. -10° C.; 21.67° C.; 64.4° F.; 195.8° F. RULE III.-To express degrees Réaumer in Centigrade, multiply by ; and, conversely, to change Centigrade to Réaumer, multiply by §. Formulas: C. = §R. R. = C. 40° R. WRITTEN 10 OPERATION 2. 50° C. × = 40° R., Ans. EXERCISES. 3. Express in Centigrade 36° R.; 80° R.; 120° R.; Ans. 45° C.; 100° C.; 150° C.; 50° C. 4. Express in Réaumer 80° C.; 160° C.; 320° C.; 60° Ans. 64° R.; 128° R.; 256° R.; 48° R. PRACTICAL MEASUREMENTS. 185. These Practical Measurements include measures of surface, volume, capacity, lumber, wood, stone and brick work, shingles, laths, plastering, painting, and carpeting. 186. A Line is that which has only one dimension, length. 187. A Surface is that which has two dimensions, length and breadth. When it does not change its direction, it is called plane. 188. A Polygon is a portion of a plane surface bounded by straight lines. 189. The Perimeter of a polygon is the sum of all its bounding lines, or sides. B 190. The Area of a polygon is the surface included within its sides. 191. An Angle is the opening or inclination of two straight lines meeting each other in a common point, called the vertex; as A BAC. Angles are either right, acute, or obtuse. A Right Angle is an A Right Angle is an angle of 90 degrees. An Acute Angle is less than a right angle; and an Obtuse Angle is greater than a right angle. 192. A Perpendicular Line is a line drawn to meet another in such a manner as to incline no more C B to one side than to the other. The two adjacent angles thus formed are equal, and are called Right Angles. In the figure, the line CD is perpendicular to AB, and the angles ADC and BDC are equal, and right angles. 193. A Rectangle is a polygon bounded by four straight lines and having four right angles. 194. A Square is a rectangle which has all its sides equal. 195. A Solid, or volume, is that which has length, breadth, and thickness, or height. The plane surfaces bounding a solid are called Faces. 196. A Cube is a solid bounded by six equal squares. |