TABLES OF SATURATED STEAM. Weight in pounds of 1,000 cubic feet of saturated steam, or the weight in pounds of water vapor in 1,000 feet of saturated atmosphere, at a temperature from 32° up to 121°. 76 67 74 66 70 64 66 62 63 61 59 59 55 57 52 55 48 53 45 58 52 56 49 54 45 59 53 57 49 55 46 77 68 74 67 71 65 67 63 63 62 59 60 56 78 69 75 68 71 66 67 65 63 63 60 61 56 79 70 75 69 71 67 68 66 64 64 60 62 57 61 53 59 50 57 47 80 72 75 70 72 68 68 67 64 65 61 81 73 76 71 72 70 68 68 65 66 61 65 58 63 54 61 51 59 48 This dew-point and relative humidity table is calculated from a barometric pressure of thirty inches. I have arranged this table for a difference of 8°, running from 60 up to 14° between the wet and dry bulbs, and in temperature from 70° up to 90°. By the use of these tables we can by a little study read the temperatures and work out the amount of water vapor in the atmosphere very readily. Suppose I go to my thermometer, and it stands at 76, 66. Now, by consulting the dew-point table, I find, in the column marked 10, 61, 59. Then the reading would be 76 dry, 66 wet, 61 dew-point and 59 relative humidity. I find by this that the atmosphere is moistened a little more than one-half it is capable of containing. Now, by looking at the table of saturated steam, we see that at 76° temperature the air is capable of holding 1.39 pounds of water in each 1,000 cubic feet of air; but, as it is only 59 per cent. saturated, we see at once that the air contains only 0.85 pound; in other words, if we consult our dew-point and humidity table, we shall find that a relative humidity of 59 gives a dew-point of 61. Now, by looking at the table of saturated steam, we find, opposite a temperature of 610, 0.85 pounds. So, if we multiply this by 7.000 (the number of grains in a pound), and divide by 1,000 (the number of cubic feet used as a basis), it will give us the number of grains contained in one cubic foot of air, -0.85 x 7.000 5.950÷ 1.000 5.950 grains water vapor. To ascertain the relative humidity from the tables: the weight of 1,000 feet of saturated steam at 61° is 0.85 pound, and at 76° it is 1.39 pounds; now, if we divide 85 by 139, we ascertain the per cent. of relative humidity in the air. Dew-Point and Absolute Humidity, in Grains. 4.527 4.686 4.850 5.018 5.192 5.371 5.526 6.350 6.564 6.784 7.010 7.243 7.483 7.728 70 7.981 8.241 8.509 8.784 9.067 9.358 9.657 9.964 10.279 10.603 3.539 3.668 3.801 3.937 By the use of this table anyone can ascertain at a glance ATMOSPHERIC CHANGES. Atmospheric changes in the mills are frequently of great dropped in weight from 2.2 on the heavy side down to 3.7 per cent. on the light side, with a loss in weight of sample of 1.4 per cent. We find, from this slight change of only 3° of dewpoint, that the weight of the work at the railways has varied 5.9 per cent.; while the loss of moisture in sample was 1.4 per cent., and a loss in absolute humidity of .998 grains. Again, on July 8, 6 P.M., wind south-west, fair temperature, 95 dry, 80 wet, 75 dew-point, 52 relative humidity, with 9.358 grains water vapor in cubic foot of air, weight of sample, 135.5 grains. On July 9, 6 P.M., wind north-west, clear temperature, 84 dry, 66 wet, 53 dew-point, 34 relative humidity, with 4.527 grains of water vapor in cubic foot of air, weight of sample, 133.5 grains. Loss in water vapor, 51 per cent.; loss in sample, 1.4 per cent., and variation at railway heads of 8 per cent. In presenting the result of these atmospheric changes, it is for the purpose of showing how essential it is for the welfare of the spinning and weaving that the carders keep a firm hold upon their work, so far as keeping numbers is concerned. There are two influences brought to bear upon cotton fibres. during their processes of manufacturing through the card room. One is a damp atmosphere, and another is a dry atmosphere. These have to be guarded against by the carders, in order that the spinners and weavers may not feel the effects of them. When a damp spell of weather comes on, the tendency is to let the yarn become too heavy, not because there is moisture sufficient to make it heavy, but by reason of more cotton fibres per inch of yarn spun. On the other hand, when the atmosphere becomes divested of moisture, the work at the railway heads will shade light unless watched pretty closely, and the result will be light yarn, by reason of loss of cotton fibres. Now, as a result of this there is a loss to the manufacturer in two ways. First, if the yarn is spun and warped heavy, the cloth will grade on the heavy side of standard. This entails a loss to the manufacturer, from the fact that more cotton is in the yarn than ought to be. Second, if the yarn is spun and dressed light, the weaving will also be light. There is a loss |