. Bulletin of the Department of Agriculture. Agriculture; Agriculture. 14 BULLETIN 532, U. S. DEPARTMENT OF AGRICULTURE. lars, L, likewise are provided merely for protection when the tube is detached from the end supporting block. The great length of the in- strument with the consequent attendant probability of the temperature at the two ends being different, due to one end being in the shade and the other in direct sunlight, led to the use of two gauge tubes of different materials from which to take measurements. Knowing the coefficients of expansion of these tubes, ob- tained by proper
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. 14 BULLETIN 532, U. S. DEPARTMENT OF AGRICULTURE. lars, L, likewise are provided merely for protection when the tube is detached from the end supporting block. The great length of the in- strument with the consequent attendant probability of the temperature at the two ends being different, due to one end being in the shade and the other in direct sunlight, led to the use of two gauge tubes of different materials from which to take measurements. Knowing the coefficients of expansion of these tubes, ob- tained by proper calibration, the difference in the microm- eter readings furnished a means of obtaining the tem- perature of the bars. This temperature then could be used in correcting the microm- eter measurements to a stand- ard temperature. Thermom- eters were inserted in the 2- inch casing at the ends of the instrument. The mean of these end temperature read- ings, as a rule, approached within 1° C. of the tempera- ture obtained from the mi- crometer readings. Before using this instru- ment on the road it was cali- brated in order to obtain the coefficients of expansion of the steel and brass tubes. In do- ing this a 10-foot steel gauge bar was mounted in a tank of water and immersed about 1 inch below its surface. Ther- mometers were laid in the Water on top of the gauge bar and read from time to time. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original United States. Dept. of Agriculture. [Washington, D. C. ?] : The Dept. : Supt. of Docs. , G. P. O.
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