368. Had the publication of this work been delayed, say two years longer, perhaps it would then be possible to ignore the old systems of weights and measures entirely, and substitute those after the metrical system in their place. To do it now, would have caused an outcry against it, and a great deal of inconvenience beside. Hence the old system has been largely adhered to. But to be at least alongside with the tendency of the age, the following tables have been carefully prepared to enable American photographers to convert foreign photographic formulae into such weights and measures as they are familiar with.

Table for Converting Cubic Centimetres into Fluid Ounces, Fluid Drachms, and Minims.

 Cubic Centimetres. Fluid Ounces. Fluid Drachms. Minims. 1= ................ ................ 16 2 = ................ ................ 32 8 = ................ ................ 49 4 = ................ 1 5 5.= ................ 1 21 6= ................ 1 37 7= ................ 1 54 8= ................ 2 10 9= ................ 2 26 10= ................ 2 42 15= ................ 4 3 20= ................ 5 25 25= ................ 6 46 30= 1 0 7
 Cubic Centimetres. Fluid Ounces. FluidDrachms. Minims. 35= . 1 1 . 28 40= . 1 . 2 . . 49 45= . 1 . 4 . 10 50= . 1 . 6 . . 31 55= . 1 6 . 52 60= . . 2 . 0 . . 14 65= . . 2 . . 1 . 36 70= . . 2 . . 2 . . 56 75= . . 2 . . 4 . 13 80= . . 2 . 5 . 38 85= . . 2 . . 7 . 90= . . 3 . . 0 . . 20 95= . . 3 . 1 . 42 100= . . 3 . 8 3

1000 c.c. = 1 litre = 34 fl. oz. nearly, or 21/8 pints.

Rules for Converting the Centigrade Scale into the Fahrenheit Scale. - If above the freezing point of water (32°), degrees X 9 5 + 32. If below the freezing point and above zero, 32 - (degrees X 9 - 5). If below zero, - (degrees X 9 - 5). (342)

Relation of metrical Weights to Troy Weight.

 Metrical weights. Equivalents in Grains. Equivalent is Grains. MlLligrames. 1 = .0154 . . . 1/55 3 = .0808 . . . 1/12 8 = .0468 . . . 1/12 4 = .0617 . . . 1/16 6 = .0771 . . . 1/13 6 = .0926 . . . 1/11 7 = .1080 . . . 1/5 8 = .1284 . . . 1/8 9 = .1889 . . . 1/7 Crntigrammes. 1 = .1543 . . 1/4 2 = .3086 . . . 1/2 3 = .4630 . . . 5/14 4 = .6178 . . . 1/11 5 = .7717 . . . 3/4 6 = .9260 . . . 1/15 7 = 1.0808 . . . l 8 = 1.2347 . . . 1 1/4 9 = 1.3890 . . . 1 1/2 10 = 1.543 . . . 1 1/2 20 = 3.086 . . . 3 80 = 4.630 . . . 4 1/2 40 = 6.173 . . . 6 50 = 7.717 . . . 7 1/2 60 = 9.260 . . . 9 70 = 10.803 . . . 11 80 = 12.347 . . . 12 1/2 90 = 13.890 . . . 14 100 = 15.433 . . . 15 1/2
 MetricalWeights. Eauivalens la Grains. Drm. Go. Oz. Drm. Grs. Crammes. 1 = 15 1/2 = ...... ..... ...... ...... ...... 2 = 81 = ...... ..... ...... ...... ...... 8 = 46 = ...... ..... ...... ...... ...... 4 = 62 = 1 2 ...... ...... ...... 5 = 77 1/2 = 1 17 1/2 ...... ...... ...... 6 = 92 1/2 = 1 82 1/2 ...... ...... ...... 7 = 108 = 1 45 ...... ...... ...... 8 = 128 1/2 = 2 3 1/2 ...... ...... ...... 9 = 189 = 2 19 ...... ...... ...... 10 = 154 1/2 = 2 34 1/2 ...... ...... ...... 11 = 169 1/2 = 2 49 1/2 ...... ...... ...... 12 = 185 = 3 5 ...... ...... ...... 18 = 200 = 3 20 ...... ...... ...... 14 = 216 = 3 36 ...... ...... ...... 16 = 281 = 3 51 ...... ...... ...... 16 = 246 1/2 = 4 6 1/2 ...... ...... ...... 17 = 262 = 4 22 ...... ...... ...... 18 = 277 = 4 37 ...... ...... ...... 19 = 298 = 4 53 ...... ...... ...... 20 = 808 1/2 = 6 8 1/2 ...... ...... ...... 80 = 462 1/2 = 7 42 1/2 ...... ...... ...... 40 = 617 = 10 17 = 1 2 17 60 = 771 1/2 = 12 51 1/2 = 1 4 51 1/2 60 = 926 = 15 26 = 1 7 26 70 = 1080 = 18 34 = 2 2 . . 80 = 1234 1/2= 20 34 1/2 = 2 4 34 1/2 90 = 1889 = 28 9 = 2 7 9 100 = 1648 1/2 = 26 48 1/2 = 8 1 43 1/2 1000 = 1 kilogramme = 82 ok. Troy.

Table for Converting Millimetres into Inches and Fractions of an Inch.

To reduce Millimetres to Centimetres, divide by 10.

1 Metre - 39.37 inches. 1 Kilometre = 0.62137, or 5/8 of a mile.

 1 Millimetres =1/24 inch. 2 " =1/12 " 3 " =1/8 " 4 " =1/6 " 6 1/2 " =1/4 " 8 1/2 " =1/3 " 9 1/2 " = 3/8 " 10 1/2 " =5/12 " 13 " = 1/2 " 15 " = 7 /12 "
 16 Millimetres = 5/8 inch. 17 " =2/3 " 19 " 3/4 " 21 " = 5/6 " 22 " =7/8 " 7/8 " =11/12 " 25 1/2 " =1 " 51 " =2 " 76 " = 83 " 101 1/2 " = 4 "
 127 Millimetres = 5 inches. 152 " = 6 " 178 " = 7 " 206 " = 8 " 228 1/2 " = 9 " 254 " =10 " 279 1/2 " = 11 " 305 " =12 "