EXPLANATIONS.

Polarization.—Most essential oils, and the solutions of several substances described in this book are capable of effecting the deviation of a ray of polarized light. The amount of this rotatory power cannot be regarded as constant in essential oils, and is greatly influenced by various causes. As to alkaloids and other organic compounds, the deviation frequently depends upon the nature and quantity of the solvent. The authors have thought it needful to record in numerous cases the results of such optical investigations, as determined by means of the Polaristrobometer invented by Wild, and described in Poggendorff’s Annalen der Physik und Chemie, vol. 122 (1864) p. 626; or more completely in the Bulletin de l’Académie impériale des Sciences de St. Pétersbourg, tome viii. (1869) p. 33.

Measurements and Weights.—The authors regret to have been unable to adopt one standard system of stating measurements. They have mostly employed the English inch: the accompanying woodcut will facilitate its comparison with the French decimal scale. The word millimetre is indicated in the text by the contraction mm.; micromillimetre, signifying the thousandth part of a millimetre, and only used in reference to the microscope, is abbreviated thus, mkm.

1 inch= 25·399 millimetres.
1 gallon= 4·543 litres.
1 ounce (oz.) avdp.= 28·34 grammes.
1 lb. avoirdupois= 453·59 ”
1 cwt.= 112 lb.= 50·8 kilogrammes.
1 ton= 2240 ”= 1016 ”
1 kilogramme= 2·204 lb. avoirdupois.
1 pecul= 133·33 lb.= 60·479 kilogrammes.

Thermometer.—The Centigrade Thermometer has been alone adopted. The following table is given for comparing the degrees of the Centigrade or Celsius Thermometer with those of Fahrenheit’s Scale.

THERMOMETRIC TABLE.

CENT. FAHR. CENT. FAHR. CENT. FAHR. CENT. FAHR.
-29° -20·2°+41° + 105·8°+111 +231·8+181 +357·8
28 18.442 107.6112 233.6182 359.6
27 16.643 109.4113 235.4183 361.4
26 14.844 111.2114 237.2184 363.2
25 13.045 113.0115 239.0185 365.0
24 11.246 114.8116 240.8186 366.8
23 9.447 116.6117 242.6187 368.6
22 7.648 118.4118 244.4188 370.4
21 5.849 120.2119 246.2189 372.2
20 4.050 122.0120 248.0190 374.0
19 2.251 123.8121 249.8191 375.8
18 - 0.452 125.6122 251.6192 377.6
17 + 1.453 127.4123 253.4193 379.4
16 3.254 129.2124 255.2194 381.2
15 5.055 131.0125 257.0195 383.0
14 6.856 132.0126 258.8196 384.8
13 8.657 134.6127 260.6197 386.6
12 10.458 136.4128 262.4198 388.4
11 12.259 138.2129 264.2199 390.2
10 14.060 140.0130 266.0200 392.0
9 15.861 141.8131 267.8201 393.8
8 17.662 143.6132 269.6202 395.6
7 19.463 145.4133 271.4203 397.4
6 21.264 147.2134 273.2204 399.2
5 23.065 149.0135 275.0205 401.0
4 24.866 150.8136 276.8206 402.8
3 26.667 152.6137 278.6207 404.6
2 28.468 154.4138 280.4208 406.4
- 1 30.269 156.2139 282.2209 408.2
0 32.070 158.0140 284.0210 410.0
+ 1 33.871 159.8141 285.8211 411.8
2 35.672 161.6142 287.6212 413.6
3 37.473 163.4143 289.4213 415.4
4 39.274 165.2144 291.2214 417.2
5 41.075 167.0145 293.0215 419.0
6 42.876 168.8146 294.8216 420.8
7 44.677 170.6147 296.6217 422.6
8 46.478 172.4148 298.4218 424.4
9 48.279 174.2149 300.2219 426.2
10 50.080 176.0150 302.0220 428.0
11 51.881 177.8151 303.8221 429.8
12 53.682 179.6152 305.6222 431.6
13 55.483 181.4153 307.4223 433.4
14 57.284 183.2154 309.2224 435.2
15 59.085 185.0155 311.0225 437.0
16 60.886 186.8156 312.8226 438.8
17 62.687 188.6157 314.6227 440.6
18 64.488 190.4158 316.4228 442.4
19 66.289 192.2159 318.2229 444.2
20 68.090 194.0160 320.0230 446.0
21 69.891 195.8161 321.8231 447.8
22 71.692 197.6162 323.6232 449.6
23 73.493 199.4163 325.4233 451.4
24 75.294 201.2164 327.2234 453.2
25 77.095 203.0165 329.0235 455.0
26 78.896 204.8166 330.8236 456.8
27 80.697 206.6167 332.6237 458.6
28 82.498 208.4168 334.4238 460.4
29 84.299 210.2169 336.3239 462.2
30 86.0100 212.0170 338.0240 464.0
31 87.8101 213.8171 339.8241 465.8
32 89.6102 215.6172 341.6242 467.6
33 91.4103 217.4172 343.4243 469.4
34 93.2104 219.2174 345.2244 471.2
35 95.0105 221.0175 347.0245 473.0
36 96.8106 222.8176 348.8246 474.8
37 98.6107 224.6177 350.6247 476.6
38 100.4108 226.4178 352.4248 478.4
39 102.2109 228.2179 354.2249 480.2
40 104.0110 230.0180 356.0250 482.0