None
194400 24 „' f 1 191000 ,1 105 „ f» S54000 CUSO4 45 „ 22° 202410 105 „ 9t 339341 HCl 15 „ 23° 13626 ^, 500 „ tt 86679 Nitric Acid (edm.) 16000 Copper Sulphate 20 per cent. 20° 170000 Zinc » 30 TABLE 245. 216000 Eesistances of Metals (J. 0. Maxwell). " In the following Table B is the resistance in Ohms of a column 1 metre long, and 1 gramme weight, at 0° 0. ; and r is the resistance in centimetres per second of a cube of one centimetre, according to the experiments of Matthiessen." Specific Gravity. Silver 10-50 hard drawn Copper 8-95 „ Gold 19-27 Lead 11-391 pressed Mercury 13-595 liquid Gold 2, Silver 1 15-218 hard or annealed 1-668 Sdenium at 100° C. crystalline form Percentage Increment of Besistance for B. r rcatao'c. 0-1689 1609 0-877 0-1469 1642 0-388 0-4160 2154 0-365 2-257 19847 0-387 13-071 96146 0-072 i 1-668 10988 0-065 6xl0i» 1-00 TABLES. 237 TABLE 24c. Electromotive Foeoe of Constant Batteeies (J. C. Maxwell). Daniell I. Amalgamated Zinc HjS04+4Aq ■ > II- » „ ■H2Aq „., III. Bunsen I, „ .. II. Grove „ Concentrated Solution of CUSO4 Copper CUSO4 „ CulJ'O, HKO, Carbon + » sp. gr. 1-38 „ + 4Aq HlSOa Platinum A Volt. = 1 ^■^^^- . (See pp. 202, 240.) Volt 1-079 0-978 1-00 1-964 1-888 1-956 TABLE 25. COMPAEISON OF MeASUEES OF ElECTEIO CtTEEENT-STEENGTH. A Cniieni-Strengtli which is measured in— Must be multiplied by the following Numbers to reduce it to — Cubic Cm. Water Oases per Minute. ■ Mgr. Water per Minute. Mgr. Copper per Minute. Silver ' per Minute. Magnetic Measure Mm.* Mgr.* Sea." Cub. Cm. Water Gases per min Mgr. Water per min.. Mgr. Copper „ Mgr. Silver ,, Magnetic Measure Mm.*Mgr.* See." • • • 1-865 0-S294 0-1555 1-044 0-5363 0-2839 0-0834 0,-5599 1889 3-522 0-2937 1-972 6-432 11-99 3-405 6-714 0-9579 1-786 0-5071 01489 TABLE 25a. BiEMiNGHAM WrEB Gatjge (HoltzapfiFel). Diameter in BWQ. Diameter in Bwa. Diameter In inches. inches. inches. 0-340 14 0-083 28 0-014 2 •284 16 •065 30 •012 4 ■238 18 •049 82 •009 « •203 20 •035 33 •008 8 •165 22 •028 34 •007 10 •134 24 •022 85 •006 }2 •109 26 •018 86 •004 238 TA6LES. TABLE 255, Mean Speoii'io Heats of Watee aitd Platinttm. Water (Regnault). Platinum <PonilletX' From 0° to 40° C. 1-0013 „ „ 80 1-0036 „ . „ 120 1-0067 „ „ 160 1-0109 „, ,, 200 1-0160 „ „ 230 , 1-0204 From 0° to 100° C. 0-0335 „ „ 300 0-0343 „- „ 500 0-0362 „ „ 700 0-0360 „ „ 1000 0-0373 „ ,; 1200 0-0382 TABLE 25c. Heat of Combustion, in Oxygen (Stewart). Grammes of Substance bnmed. Water raised 1* C. by Combination of 1 Gramme. . jCompound formed. Observer. Hydrogen .... 34462 OH, Favre and Silbermann. tt ' 33808 »| ' Andrews. Caiton 8080 CO, Favre and Silbermann. »» • 7900 it Andrews. Sulphur 2220 so. Favre and Silbermann. »j • 2307 tf Andrews. Phosphonis 5747 PA tt Zinc . .. 1301 ZnO Iron . .. 1576 Fefii jj Tin . .. 1233 SnO, jj Copper .. 602 CuO tt Carbonic Oxide (CO) 2431 CO, tt tf 2403 t* Favre and Silbermann. Marsh Gas (CHJ. 13063 CO, + 20H, ff tt »» ■ 13108 »f Andrews. defiant Gas (CjHJ. 11942 2C0, + 20H, »» tt ' 11858 tt Favre and Silbermann. Alcohol (CjHjHO). 6860 2C0, + 30Ha Andrews. )) 7183 f) Favre and Silbermann. Heat of Comb trsTioN IN Chi iORINE. Hydrogen . . . . | 23783 HCl Favre and Silbermann. Eotassium. 2655 KCl Andrews. Zinc • • • 1529 ZnCl Fe,Cla Iron . .. 1745 Tin , .. 1079 SnCL .. Antimony. 707 SbCl, • Arsenic . .. 994 AsCl, Copper . .. 961 CuCl, TABLES. 239 TABLE 26. Symbols, Atomic Weight, Valence, and Specific Heat of soMB Elements. The Atomic Weight is the smallest proportion in ■which the element enters into combination ; hydrogen being taken as 1. The Valence or Atomicity indicates the niunber of atoms of hydrogen 01 other univalent ^lenient -which one atom wiU replace or combine with. In some cases the element a|Cts as if its valence were less by 2 or 4 than that given. Equal quantities of electricity liberate equal valences. Specific Heat multiplied by atomic weight is nearly constant for the same physical state in all elements. The Electro-negative elements, or those which in electrolysis appear at the positive pole or zincode, are printed in italics; the electro posi- tive, or those which appear at the negative pole or platiuode, in Boman type.' The difference, Jiowever, is only one of degree. Name. Symbol. Atomio Weight Valence. , Specific Heat of Equal Parts. Almtiinium . .. AI 27-5 VI. III. 0-2143 Antimony Sb 122 Y. 0-0508 Arsenic As 75 V. 0-0814 Barium. Ba 137 II. Bismuth. Bi 208 V. 0-0308 Boron .. B, 11 IV. Bromme. .. Br 80 I. 0-1060 Liquid. 0-0843 SoHd. Calcium. Ca 40 II. Carbon C 12 ' IV. I 0-2415 Charcoal, j 0-1468 Diamond. Chlorine. CI 35-5 I. 0-1210 Const, press. Chromium Cr 52-5 VI. Cobalt .. Co 58-8 VI. 0-1070 tr: : Ou 63-5 II. 0-0951 Au 196-7 III. 0-0324 Hydrogen. H 1 I: 8-4090 Const, press. Iodine .. I 127 I. 0-0541 Iron .. Fe 56 VI. III. 0-1138 Lead. .. Pb 207 IV. 0-0314 Magnesitim Mg 24 II. 0-2499 Manganese Mu 65 VI. III. 0-114 Mercury. Hg 200 II. 0-0319 Solid. Nickel .. Ni 68-8 VI. III. 0-1091 Nitrogen. N 14 V. 0-2438 Const, press. Oxygen. 16 II. 0-2175 Phosphorus P 31 V. Platinum .. Pt 197-4 IV. 0-0324 Potassium. K 39 I. 0-1696 Silicon .. Si 28-5 IV. Silver .. Ag 108 I. 0-0570 Sodium. nI 23 I. 0-2934 StroBtium. Sr 87-5 II. Sulphur. S 82 VI. 0-1776 Tin . ,. Sn 118 IV. 0-0562 Zino .. ■Zn 65 II. 0-0965 240 TABLES. TABLE 27. NUMBEES FEBQTJENTLY EEQITIEED. (The fractions in brackets are approximate values.) ■■ = 3-1416 (V), T= = 9-870, I = 0-3183, Z= -7854, log jt =0-4971499.' 5r 4 The modulus of natural logarithms = 2-3026. i The angle c£ which the arc is equal to the radius = 57°-2958 = 3437 •'75 = 206265". Eatio of the probable to the mean error = 0-67449 (|). 1 Paris foot = 0-32484 metre (H)- 1 metre = 3-0784 Paris feet 1 Paris line =2-2588 mm. (f). 1mm. = 0-44330 Paris line. 1 Ehenish foot= 0-31385 metre (M). 1 metre = 3-1862 Ehenish feet 1 English foot = 0-30479 „ (A). 1 metre = S -2809 English feet IGer. mile = 7 -4204 kUom. ( V). 1 kiL = 0-13476 Ger. mUe. 1 English mile= 1-60929 „ 1 kil = 0-62138 Englishmilfid). Half the major axis of the earth = 6377400 metres. „ minor „ = 6356100 „ The mean semidiameter of „ = 6366800 „ Accelerative force of Gravity. Length of Seconds Fenduhuil* At 45° latitude 9806 mm. = ft 993-5 mm. ,, the equator 9780 ,, 990-9 ,, „ the poles 9832 „ 996-2 „ Mean length of civil year 365 dy. 5 hr. 48 m. 48 sec. Velocity of sound at 0° C. in dry air = 330 ^^ The coefficient of expansion of gases 0-003665 (^fs). Latent heat of water = 79-4. Latent heat of steam at 100° C. = 540. Specific heat of air at constant pressure = 0-237. Atomic weight divided by vapour-density, compared to air, gives 28-88. Vapour-density compared to hydrogen = molecular weight. 1 litre of hydrogen at 0° and 760 mm. weighs 0-0896 grm. Mechanical equivalent of heat — 1 lb water heated 1° Eahr. = 772 foot pounds. 1 lb „ 1° C. = 1390 „ 1 grm _ „ 1° C. = 424 gramme metres = 4157 . ^^' ^"°' A galvanic current of 1 — 5i^^ — SEll decomposes 0-560 mgr. of water per minute. Siemens's mercury unit of resistaaoe is in absolute measure -9705 Ohm or B A unit. 1 Ohm = 1 ^^'th quadrant _ ..y Metre Second Seconds' 1 Volt.= 100000 absolute electromagnetic units of tension, or 1 — i — Sl. Sec' Wave-length of sodium light (D. Fraunhofer) = 0-0005895 mm. A plate ot quartz mm. tmck rotates the plkne of polarisation of sodium fight 21° -67. TABLES. 241 TABLE 28. Sqttakes, Squaee Boots, and Eecipeocals. ' II. ««. A/,r n' «. »>. VST 1 n' 1 1 1-000 I'-OOOO 50 2500 7-071 0-0200 2 4 1-414 0-5000 51 2601 7-141 0-0196 8 9 1-732 0-3333 52 2704 7-211 0-0192 4 16 2-000 0-2500 53 2809 7-280 0-0189 6 26 2-236 0-2000 54 2916 7-348 0-0185 6 36 2-449 0-1667 55 3025 7-416 0-0182 7 49 2-646 0-1429 56 8136 7-483 0-0179 8 64 2-828 0-1250 57 3249 7-550 0-0175 9 81 8-000 0-1111 58 3364 7-616 0-0172 10 100 3-162 0-1000 59 3481 7-681 0-0169 H 121 3-317 0-0909 60 3600 7-746 0-0167 12 144 3-464 0-0833 61 3721 7-810 0-0164 13 169 8-606 0-0769 62 3844 7-874 0-0161 14 196 3-742 0-0714 63 3969 7-937 0-0159 15 225 3-873 0-0667 64 4096 8-000 0-0156 16 256 4-000 0-0625 65 4225 8-062 0-0154 17 289 4-123 0-0588 66 4356 8-124 0-0152 18 324 4-243 0-0556 67 4489 8-185 0-0149 19 361 4-369 0-0526 68 4624 8-246 0-0147 20 400 4-472 0-0500 69 4761 8-307 0-0145 21 441 4-583 0-0476 70 4900 8-367 0-0143 22 484 4-690 0-0455 71 5041 8-426 0-0141 23 529 4-796 0-0435 72 5184 8-485 0-0139 24 576 4-899 0-0417 73 5329 8-544 0-0137 25 625 5-000 0-0400 74 5476 8-602 0-0135 26 676 5-099 0-0385 75 5625 8-660 0-0133 27 729 5-196 0-0370 76 5776 8-718 0-0132 28 784 5-292 0-0357 77 6929 8-775 0-0130 ' 29 841 5-385 0-0345 78 6084 8-832 0-0128 i 30 900 5-477 - 0-0333 79 6241 8-888 0-0127 31 961. TABLE 29. — Teigonometeical Functions. Angle. Sine. Tangent, Cotangent, Cosine. 0° 1 2 3 4 6 6 7 8 9 10° 11 12 13 14 15 16 17 18 19 20° 21 22 23 24 25 26 27 28 29 30° 31 82 33 34 35 86 37 40° 41 42 43 44 45° 0-000 0-017 0-035 0-052 0-070 0-087 0-105 0-122 0-139 0-156 0-174 0-191 0-208 0-225 0-242 0-259 0-276 0-292 0-309 0-326 0-342 0-358 0-375 0-391 0-407 0-423 0-438 0-454 0-469 0-485 0-500 0-615 0-530 0-545 0-559 0-674 0-588 0-602 0-616 0-629 0-643 0-656, 0-669 0-682 0-696 0-707 17 18  13 12 0-000 0-017 0-035 0-052 0-070 0-087 0-105 0-123 0-141 0-158 0-176 0-194 0-213 0-231 0-249 0-268 0-287 0-306 0-325 0-344 0-364 0-384 0-404 0-424 , 0-445 0-466 0-488 0-510 0-532 0-554 0-577 0-601 0-626 0-649 0-675 0-700 0-727 0-754 0-781 0-810 0-839 0-869 0-900 0-933 0-966 1-000 17 18 17 18 17 18 18 18 17 18 18 19 18 18 16 19 19 19 19 20 20 20 20 21 21 22 22 22 22 23 24 24 24 26 26 27 27 27 29 29 30 31 33 32 35 00 57-29 28-64 19-08 14-30 11-43 9-514 8-144 7-115 6-314 6-671 5-145 4-705 4-331 4-011 3-732 3-487 3-271 3-078 2-904 2-747 • 2-605 2-475 2-356 2-246 2-145 2-050 1-963 1-881 1-804 1-732 1-664 1-600 1-640 1-483 1-428 1-376 1-327 1-280 1-236 1-192 1-150 1-111 1-072 1-036 1-000 811 643 526 440 374 320 279 245 216 193 174 157 142 130 119 110 101 95 87 82 77 73 67 64 60 57 55 52 49 47 45 43 42 39 39 86 36 1-000 1-000 0-999 0-999 0-998 0-996 0-995 0-993 ,0-9?0 0-988 0-985 0-982 0-978 0-9,74 0-970 0-966 0-961 0-966 0-951 0-946 0-940 0-934 0-927 b-921 0-914 0-906 0-899 0-891 0-883 0-875 0-866 0-857 0-848 0-839 0-829 0-819 0-809 0-799 0-788 0-777 0-766 0-756 0-743 0-781 0-719 0-707 11 12 12' 12 12 90° 89 88 87 86 85 84 88 82 81 80° 79 78 77 76 75 74 73 72 71 70° 69 68 67 66 65 64 63 62 61 60° 59 58 67 56 55 64 62 52 51 50° 49 48 47 46 46° CaeliM. Cotangent. Tangent, Sine. Angle XABLES. 243 TABLE 30. LOGABITHMS TO 4 PLACES. 1 1 2 s 4 S 6 7 8 Dlft i 10 0000 , 0043 0086 0128 0170 0212 0253 0294 0334 0374 42 11 0414 1 0453 0492 0631 0569 0607 0645 0682 0719 , ,0755 88 12 0792 , 0828 0864 0899 0934 0969 1004 .1038 1072 1106 85 13 1139 i 1173 1206 1239 1271 1303 1835 1367 1399 1430 32 14 1461 : 1492 1523 1553 1584 1614 1644 1673 1703 1782 SO 15 1761 1790 1818 1847 1876 1903 1931 1959 1987 2014 28 16 2041 2068 2096 2122 2148, 2175 2201 2227 2253 2279 26 17 2304 2330 2355 2380 2405 2430 2456 2480 2504 2529 26 18 2563 , 2577 2601 2625 2648 2672 2695 2718 2742 2765 28 19 2788 2810 2833 2856 2878 2900 2923 2946 2967 2989 22 20 3010 3032 8054 8075 8096 3118 3139 3160 3181 3201 21 21 3222 \ 3243 8263 3284 3304 3324 3345 3365 3385 8404 20 22 3424 3444 3464 3483 3502 3522 8541 3560 3679 3698 19 23 3617 3636 8666 3674 8692 8711 3729 8747 3766 8784 18 24 3802 8820 8838 3856 3874 8892 3909 3927 3945 8962 18 25 3979 3997 4014 4031 4048 4065 4082 4099 4116 4133 17 26 4150 4166 4183 4200 4216 4232 4249 4265 4281 4298 16 27 4314 4330 4346 4362 4378 4393 4409 4425 4440 4456 16 28 4472 4487 4602 4518 4538 4648 4564 4579 4694 4609 15 ;29 4624 j 4639 4654 4669 4683 4698 4713 4728 4742, 4757 15 30 4771 1 4786 4800 4814 4829 4843 4857 4871 4886 4900 14 81 4914 1 4928 4942 ,4955 4969 4983 4997 6011 5024 5038 14 32 6051 ' 6066 6079 5092 6106 5119 5132 6145 6159 •6172 13 33 5185 5198 6211 6224 5337 6250 5263 5276 5289 5302 13 34 5315 5328 6340 5353 5366 6378 5391 5403 5416 5428 13' 85 6441 5463 5466 6478 6490 5502 5514 6527 5539 5551 12 86 5563 6575 6587 6699 5611 5623 5635 6647 5658 5670 12 37 5682 5694 5706 6717 5729 5740 5752 5763 5776 5786 12 38 5798 5809 5821 .6832 5843 6855 5866 .'i877 5888 5899 11 j 39 6911 6922 6933 6944 6965 5966 6977 5988 5999 6010 11 140 6021 6031 6042 6053 6064 6076 6086 6096 6107 6117 11 j 41 6128 6138 6149 6160 6170 ,6180 6191 6201 6212 6222 10 [42 6232 6243 6253 6268 6274 6284 6294 6304 6314 6325 10. 1 2 8 4 6 e 7 8 » BUT. 244 TABLES. TABLE 30— Continued. LOOABITHMS TO 4 PLACES. HT. 1 2 S i 9 6 7 8 9 Ditt 65 7404 7412 7419 7427 7435 7443 7451 7459 7466 7474 8 56 7482 7490 7497 7505 7513 7520 7528 7536 7543 7551 8 57 7559 7666 7674 7582 7589 7597 7604 7612 7619 7627 8 58 7634 7642 7649 7657 7664 7672 7679 7686 7694 7701 7 59 7709 7716 7723 7731 7738 7745 7752 7760 7767 7774 7. 60 ' 7782 7789 7796 7803 7810 7818 7825 7832 7839 7846 7 61 7853 7860 7868 7876 7882 7889 7896 7903 7910 7917 7 62 7924 7931 7938 7945 7952 7959 7966 7973 7980 7987 7. 63 7993 8000 8007 8014 8021 8028 8035 8041 8048 8055 7 64 8062 8069 8076 8082 8089 8096 8102 8109 8116 8122 7 65 8129 8136 8142 8149 8156 8162 8169 8176 8182 8189 7 66 8195 8202 8209 8215 8222 8228 8236 8241 8243 8264 7 67 8261 8267 8274 8280 8287 8293 8299 8306 8312 8319 6 68 8325 8331 8338 8344 8351 8357 8363 8370 8376 8382. 9956 9961 9965 9969 9974 9978 9983 9987 9991 9996 4 1 2 8 i 6 e 7 8 9 MK INDEX. AasoLCTK directive force, 193 5, electromotive force, 177 „ electrostatic measure, 19i „ force measure, 192 „ galvanic measure, 199 „ ,, „ and work, 203 ,, mechanical measure, 192 ,, moment of rotation, 193 ,, resistance, 188, 203 Absorption, electric, 211 Accumulators, 210, 212 Air, density, 224 „ humidity, 71, 229 Amp&rA's law, 200 Analysis, spectrum, 97 Angles of crystals, 90 „ of prisms, 9i „ of deviation, 95 Angular measurement, 114, 116 Approjdmation-formulie, 10 Aqueous vapour tension, 71, 228, 229 Arc, infinitely small arc, 124, 233 Areometry, 36 Arithmetical mean, 1 Atmospheric pressure, 51, 228 Auguste's psychrometer, 73 Balance, 20 ; Mohr's, 36 „ oscillation of, 23 ,, sensitiveness, 26 ,, ratio of arms, 27 Bar magnetism, 146, 194 Barometer, 51, 63, 228 Battery, Internal resistance of, 170, 214 B A unit, 203, 2^0 Bifilar galvanometer, 144 „ magnetometer, 180 Birmingham wire-gauge, 237 Boiling temperature of fluids, 70 ,, temperature! of water, 227 Bossoha's method of compensation, 175 Bottle, specific gravity, or pyknometer, 30, 38 Breaking strains, tahle of, 230 Browning's direct-vision spectroscopes, 207. Bunsen's ice-calorimeter, 79. Bunsen and Kirchhoff's scale, 98, 231 Calculation, numerical, 20 17 Calculation of corrections, 16 Calibration of thermometers, 57 Calorimeter, Bunsen's, 79 Calorimetry, 74 Camera Incida, 110 Capacity, electrostatic, 210 Capillary depression of mercury, 230 Chemical measure of currents, 157 Chronoscopy, 218 Circle, torsion, 129 Clark's potentiometer, 214 Cocoon fibres, 134, 135 Coefficient of torsion, 128, 134 „ of galvanometer coil, 154, 160 Commutator, 151, 211 Comparison of horizontal force, 143 ,, of thermometers, 64, 67 Compass, surveying with, 134 ,, tangent, 9, 150 „ sine, 152 Compensated magnetometer, 142 Compensation methods, 175. Condensers, 210, 212 Conductivity for heat, 81 Constants, empirical, ,11 Corrections, calculation of, 16 Crystals, angular measurement, 90 Cubical dilation, 69 Currents, derived, 149 „ Ohm's laws of, 148 „ measure of gaivanic,^150, 152, 163, 154, 157 „ , , of short duration, 181 „ ,, absolute measure of, 154, 160, 199 Curvature radius, 101, 102 "Damped" needles, 118. Damping, ratio of, 118 „ resistance measured by, 168- DanieU's batteiy, 149, 162, 209,- 237 „ hygrometer, 72 Declination, magnetic, 132, 141, 284,' 2Sr Decrement, logarithmic, 119 Density, 35, 40, 43, 221 of gases, 35, 44, 45, 61, 221 „ of liquids, 36, 221 of vapout, 45, 50 „ of water, 223 246 INDEX Density of air, 224 Derived measuree, 189 „ currents, 149 Deviation, minimum, 95 Differential galvanometer, 164 ,, voltameter, 217 Diffraction spectrum, 100 Dilatation, coeSBoient of, 69 Dimensions of a unit, 191 Dip, magnetic, 129 Directive force, 193 Dumas's method, 45 Dust figures, Kundt's, 90 Eakth-ihddotor, 184 Elasticity, modulus of, 83, 23,0 Electrometers, Thomson's, 208 Electromotive force, 161, 177, 201, 237 Electrolytes, resistance of, 170, 236 Electrostatic measure, 195 „ capacity, 210 Elements, table of, 239 Empirical constants, 11 Equilibrium, position of, 117 En-ors, constant, 2 „ of observation, 1 „ mean and probable, 1, 2 „ influence of, on results, 4 Expansion of water, 223 Factor, reduction of galvanometer, 154, 160 Fastre's thermometers, 64 Field of view, 109 " First positiou," 136, 195 Fluids, boiling point of, 70, ' „ sp. 247 tiUcida, camera, 110 Lussao's, Gay, method for vapour-density,. 60 Magnetio absolute measure, 135, 154, 189, 194 „ declination, 132, 141, 234, 235 „ horizontal force, 135, 197, 234, 235 „ horizontal force by galvanic methods, 179 „ inclination, 129, 184 „ needle, 117 Magnetism of bar, 146, 194 Magnetisation of needle, 132 Magnetometer, bifilar, 144 „ compensated, 142 „ Kew unifilar, 141 „ Weber's, 139 Magneto-inductor, 187 Magnifying power, 107 Mance's method, 214 Mariotte's law, 43 Mean error, 1 Measurement, angular, 114 Measures, absolute, 135, 154, 177, 189 „ derived, 189 „ electrostatic, 194 „ galvanic, 199 „ magnetic, 194 „ mechanical, 192 Mechanical measures, 192 Mercury, resistance of, 203, 220, 236 „ units, 203, 205, 240 „ tension of vapour, 230 „ capillary depression, 230 Microscope, 109 "Middle scale-division," 115 Millimetres to inches, table, 229 Minimum deviation, 95 Mirror, Wheatstone's revolving, 220 „ galvanometer, 153 Mirror and scale, 115 Modulus of elasticity, 83, 230 Mohr's balance, 36 Moment of inertia, 125, 193 „ rotation, 193 Multiplier, or coil, 150, 152, 163, 200 „ coefScieiit of, 154, 200 Multiplication, method of, 181 Needle, swinging, 117 Nicholson's hydrometer, 37 Nodes, 90 Numbers often wanted, 240 Numerical calculation, 20 Ohm's laws of currents, 148 Ohm or B A unit, 208, 240 Optical instruments, 107 Oscillation of balance, 23 „ by torsion, 89 „ of magnets, 117, 119, 120, 135, 142, 147 Oxygen, combustion in, 238 Paballaz, 95, 1^2 Pitch of musical notes, 231 Polarisation, rotatory. Rod, stretching of, 83, 89 ; bending, 87 Boots, square, table of, 241 Rotation, moment of, 193 Saocharimetrt, 111 Scale, Bunsen and Kirchhoff's, 98 „ telescope, mirror, and, 114 " Seoond'position " of magnet, 138, 196 Short currents, 181" Siemens's pyrometer, 216 „ unit, 203, 220, 240 Silvering glass, 115 Sine-compass or galvanometer, 152 Sines, table of, 242 Slide resistance, 213 Sodium line, 98 Soleil's saccharometer, 112 Solutions, specific gravity of, 222 Sound, length of ■waves, 89 „ velocity, 90 Specific gravity, 35 ; of solutions, 222 „ „ bottle, 36, 38 Specific heat, 74, 229, 238, 239 Spectrum analysis, 97 ,, diffraction, 100 „ refraction, 94, 97, 205 Spectra of metels, 99, 207, 231, 232 Spectrometer, 94 Spherometer, 101 Squares, least, 11 „ and square roots, 241 Stretching, modulus of elasticity by, 83, 89 Sugar, rotary polarisation of. 249 Telescope, Galilean, 109 ,, field of view of, 109 ,, mirroT and scale, 114 Temperature, by thermo-elemeut, 25 ,, inflnence on density, 14, 223 ,, by resistance, 216 „ of boiling water, 227 Tension of aqueous vapour, 228, 229 „ of mercurial „ 230 Terrestrial magnetism, declination, 132, 234, 235 „ „ Inclination, 129 „ „ horizontal force, 135, 234, 235 Thermo-element; 75 Thermometer, calibration of, 57 ,, air, 64 ,, Fastr^'s, 64 „ comparison of, 64 „ Jolly's, 65 Thickness of plates, 102 Thomson's electrometers, 208 „ galvanometers, 203 „ method for galvanometer re- sistance, 213 „ slide resistance, 213 Time of osoUlation, 119, 120, 124, 135, 140, 142, 147 „ „ reduction of, 124, 233 Torsion, 89 „ coefficient of, 128, 134 „ circle, 129 Trapdoor electrometers, 208 Turning-point, 119 Unifilab magnetometer, 139, 141 Units, absolute or derived, 189 Unit, B A or Ohm, 203, 240 Unit, Siemens's, 203, 205 „ Weber's, 154, 199, 205 ,, dimensions of, 191 Vaooo, weight in, 30, 40, 226 ,, refraction in, 96, 97 Vapour-density, 45 Velocity of soimd, 90 „ Eesistance a, 203 View, field of, 109 Voltameter, 157 „ measure of horizontal force, 179 „ differential, 217 Volumenometer, 43 Water, density of, 223 ,, boiling temperature of, 229 „ dilatation of, 223 „ tension of vapour of, 228, 229 Wave-length of sound, 90 „ of Hght, 100, 205, 232 Weber's current unit, 154, 199, 205 'Weighing, 20 „ absolute, 29 „ corrections of, 17 „ double, 29 ,, influence of errors, 7 „ by swing of balance, 23 „ by interpolation, 23 „ reduction to vacuo, 30, 40, 226 Weights, correction of, 32 Wheatstone's bridge, 165, 167, 176 ,, rotating mirror, 220 Wild's saccharimeter, 112 Wollaston's goniometer, 91 Work, absolute measure of, 192, 203 THE Ken>, SCIENTIFIC LECTURES AND ESSAYS. Popular Lectures on Scientific Subjects. By H, Hblmholtz, Professor of Physios in the University of Berlin. First Series. Translated by E. Atkinson, Ph. D., F. 0. 8. With an Introduction by Professor Ttn- DALt. "With 51 Illustrations. 12mo. Oloth, $2.00. CONTENTS.— ^io. the Relation of Natural Science to Science in General.— On Goethe's Scientific Kesearohes. — On the Physiological Causes of Harmony in Music. — Ice and Glaciers. — ^Interaction of the Natural Forces. — The Recent Progress of the Theory of Vision. — ^The Conservation of Force. — ^Aim and Progress of Physical Science. Popular Lectures on Scientific Subjects. By H. Helmholtz. Second Series. 12mo. Oloth, $1.50. CONTENTS. — Gustav Magnus. — In Memoriam. — The Origin and Significance of Geometrical Axioms. — Relation of Optics to Painting. — Origin of the Planetary System. — On Thought in Medicine. — Academic Freedom in German Universities. " Professor Helmholtz's second series of ' Popular Lectures on Scientific Subjects ' forms a volume of singular interest and value. He who anticipates a dry record of facts or a sequence of immature generalization will find himself happily mistaken. In style and method these discourses are models of excellence, and, since they come from a man whose learning and authority are beyond dispute, they may be accepted as presenting the conclufiions of the best thought of the times in scientific fields." — Boston Traveller. Science and Culture, and other Essays. By Professor T. H. HuxxBT, F. E. S. 12mo. Oloth, $1.50. " Of the essays that have been collected by Professor Huxley in this volume, the first four deal with some aspect of education. Most of the remainder are expositions of the results of biological research, and, at the same time, illustrations of the history of scien- tific ideas. 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