For these platinum is greatly to be preferred to any other known substance. Its rather high cost is the only objection to its use. Its heat capacity is low, by weight, but its specific gravity is great, and sufficient capacity can be obtained in moderate bulk, while its high conductivity tends to shorten the duration of each experiment or observation. A convenient outfit for each instrument consists of three balls, hammered to a spherical form, one 1.1385 inches diameter, weighing 4,200 grains=0.6 pound avoirdupois; one 0.9945 inch diameter, weighing 2,800 grains=0.4 pound; and one 0.7894 inch diameter, weighing 1,400 grains=0.2 pound. These can be obtained at 1-2/3 cents per grain, and will cost, respectively, $70.00, $46.67, and $23.33, and collectively, $140.00. At the assumed specific heat of Pt=0.0333+, the heat capacity of the respective balls will be 1/100, 1/150, and 1/300 of 2 pounds of cold water, and the two smaller balls used together will be equal to the larger one. Corrections for varying specific heat of platinum may be conveniently made by the tables given in a previous article.[1] Corrections for varying specific heat of water are less important, but may be made by the following table: _Temperatures, Fahrenheit, and Corresponding Number of British Thermal Units Contained in Water from Zero Fahrenheit_. _______________________________________________________________ Deg | B.t.u. || Deg | B.t.u. || Deg | B.t.u. || Deg | B.t.u. | ----+--------++-----+--------++-----+---------++-----+---------+ 32 | 32.000 || 57 | 57.007 || 82 | 82.039 || 107 | 107.101 | 33 | 33.000 || 58 | 58.007 || 83 | 83.041 || 108 | 108.104 | 34 | 34.000 || 59 | 59.008 || 84 | 84.043 || 109 | 109.107 | 35 | 35.000 || 60 | 60.009 || 85 | 85.045 || 110 | 110.110 | 36 | 36.000 || 61 | 61.010 || 86 | 86.047 || 111 | 111.113 | 37 | 37.000 || 62 | 62.011 || 87 | 87.049 || 112 | 112.117 | 38 | 38.000 || 63 | 63.012 || 88 | 88.051 || 113 | 113.121 | 39 | 39.001 || 64 | 64.013 || 89 | 89.053 || 114 | 114.125 | 40 | 40.001 || 65 | 65.014 || 90 | 90.055 || 115 | 115.129 | 41 | 41.001 || 66 | 66.015 || 91 | 91.057 || 116 | 116.133 | 42 | 42.001 || 67 | 67.016 || 92 | 92.059 || 117 | 117.137 | 43 | 43.001 || 68 | 68.018 || 93 | 93.061 || 118 | 118.141 | 44 | 44.002 || 69 | 69.019 || 94 | 94.063 || 119 | 119.145 | 45 | 45.002 || 70 | 70.020 || 95 | 95.065 || 120 | 120.149 | 46 | 46.002 || 71 | 71.021 || 96 | 96.068 || 121 | 121.153 | 47 | 47.002 || 72 | 72.023 || 97 | 97.071 || 122 | 122.157 | 48 | 48.003 || 73 | 73.024 || 98 | 98.074 || 123 | 123.161 | 49 | 49.003 || 74 | 74.036 || 99 | 99.077 || 124 | 124.165 | 50 | 50.003 || 75 | 75.027 || 100 | 100.080 || 125 | 125.169 | 51 | 51.004 || 76 | 76.029 || 101 | 101.083 || 126 | 126.173 | 52 | 52.004 || 77 | 77.030 || 102 | 102.086 || 127 | 127.177 | 53 | 53.005 || 78 | 78.032 || 103 | 103.089 || 128 | 128.182 |