TEMPERATURE AND HUMIDITY. ATMOSPHERIC CHANGES. PER CENT. OF VARIATION OF WATER VAPOR, IN GRAINS. LOSS AND GAIN IN COTTON FIBRE. By F. E. SAUNDERS, Lowell, Mass. One of the problems that our manufacturers are trying to solve is that of atmospheric changes, their effect upon cotton fibres, and the best methods to adopt in our mills in order to control them. It is safe to say that it is a very difficult question to solve, from the fact that it is of such a complex nature. For instance, the temperature and humidity in our mills may be at one point, and in a few hours a change in the weather has resulted in adding to or taking from the moisture in the atmosphere. In presenting a paper before the Manufacturers' Association, it is for the purpose of treating the subject in a practical manner, so that we may better understand how to regulate our work, when these changes take place. When a physician is called to treat a difficult disease, he at once takes a diagnosis of the case, and then applies the remedy. In the subject before us, quite a number have taken careful observations of these atmospheric changes that are constantly occurring, and yet are at a loss where to apply the remedy. The time may come when we shall be able to control these changes so far as to, in a measure, eliminate the effects of electricity. MOISTURE OF THE ATMOSPHERE. It may be of general interest at this time to give the temperatures and humidities of the several localities of Europe and America. The absolute moisture of the atmosphere varies with the temperature, both in the course of the year and of the day. In summer there is a maximum at 8 in the morning and evening, and a minimum at 3 P.M. and 3 A.M., because the ascending current of air carries the moisture upwards. The absolute is greatest in the tropics, where it represents a pressure of 25 mm; while in our latitude it does not exceed 10 mm. The relative moisture, on the other hand, is at a minimum in the hottest, and at its maximum in the coolest, part of the day. It varies also in different regions. It is greater in the centre of continents than it is on the sea or the sea-coast. That the dryness diminishes with the distance from the sea, is shown by the clearer atmosphere of continental regions. In Platowskya, Siberia, the air at a temperature of 24° was found to contain a quantity of moisture only sufficient to saturate at 3°. The air might, therefore, have been cooled through 27° without any deposit of moisture. In some parts of East Africa the springs of powder flasks exposed to the damp atmosphere snap like twisted quills; paper becomes soft and sloppy, by the loss of glaze; and gunpowder, if not kept hermetically sealed, refuses to ignite. On the other hand, in North America, where the west and north-west winds blow over large tracts of land, the moisture in the air is less than in Europe. Evaporation is, therefore, more rapid than in Europe; clothes dry quickly, bread soon becomes hard, newly built houses can be at once occupied. European pianos soon give way there, while American-built pianos are very durable on this side of the ocean. Evaporation is quicker, the drier the air, as will be observed by consulting the hygrodeik readings of the several mills. DIRECTION OF WINDS. It is a well-known fact that the temperature and absolute humidity is much evener in Lancashire, England, than in New England. The difference between the average July and the average January temperatures seems to be in Lancashire only 180, which, compared with the apparent difference of 45° in Massachusetts, is small. There is found in Lancashire a set of conditions of temperature, prevailing winds and geographical surroundings, which is hard to believe can be duplicated. The most frequent wind is that from the south-west, and this, blowing from off the Gulf Stream, is naturally full of moisture. The relative and absolute humidities run even, as compared to New England, as will be seen from the following table of temperature readings observed in Stalybridge, England, for the month of July, 1887 Water Vapor Maximum, 7.010 grains; minimum, 4.373 grains; mean, 5.581 grains. Prevailing south-west winds. It can very readily be seen from this table why there is such a uniformity of moisture and relative humidity. We find that in this month the wind blew from the south-west twenty-two days. In order to fully cover the point under discussion, I will present the following table, showing the number of days in one thousand that the wind blows from each of the eight points of the compass in Lancashire: Direction, . N., NE., E., SE., S., SW., W., NW. I will also present the following table, showing the number of days in nine hundred and sixty-five that the wind blew from each of the eight points of the compass in New England: Direction, . N., NE., E., SE., S., SW., W., NW. It will be seen from these tables that the prevailing winds of England are south-west and west, while the prevailing winds of New England are west and north-west; coming from a nonhumidity-producing region. This certainly has a very important bearing upon the great manufacturing centres of New England; as well as the fact that our temperatures and humidities are constantly fluctuating. HYGRODEIK READINGS. Wishing to compare temperature readings in different mills at the same time, I have been very kindly assisted by Messrs. WALTER E. PARKER of the Pacific, E. W. THOMAS of the Tremont and Suffolk, and J. W. KENT of the Wamsutta. These readings were carefully observed at the same hour of the day, except the Wamsutta, where the time of observation was a little later. The amount of absolute humidity has been worked out from signal-service tables, so that we can see at a glance what a cubic foot of air contains. The maximum, minimum and mean of each mill has also been worked out, so that we can see the loss and gain sustained. We find from these temperature readings that the loss and gain of water vapor in the atmosphere was as follows: Pacific, 67.76 per cent.; Wamsutta, 47.88 per cent.; Suffolk, 48.17 per cent.; Tremont, 53.43 per cent.; Hamilton, 51.62 per cent. This certainly seems to be a very large per cent., but we must take into consideration the fact that the atmospheric changes were very marked. Take, for instance, July 8 in the Hamilton Mills. At the reading 2 P.M., the thermometers indicated 9.067 grains per cubic foot of air, and at 2 P.M., July 10, 4.527 grains, or a loss of nearly 50 per cent. of moisture. We will at this time make an estimate of the loss and gain of water vapor in the Tremont Mills. The highest point reached 9.067 grains now, if we multiply the number of grains by the cubic feet of air (which we will call 300,000), and divide by 7.000 (the number of grains in a pound), we shall obtain 388 pounds of water. If we desire to carry this into gallons, we first ascertain what a gallon of water will weigh, which is 8.322 pounds. Now, if we divide 388 by 8.322, we shall get a product of 46 gallons of water contained in the room. |