_Common Thermometers._--Having, by the method which we have just described, obtained a _Standard Thermometer_, you may procure with facility as many ordinary thermometers as you desire. It is proper to employ the most regular tubes which you can obtain, and when the instruments are ready to be graduated, you must bring them into comparison with your standard thermometer. You place them together into a liquid of which you gradually raise the temperature, and you mark several points on the scale of the new thermometer, the intervals between which are subsequently divided into as many degrees as are marked on the scale of the standard thermometer. Thus, for example, you mark the 10° and 15°, and afterwards divide the interval into five equal parts. This gives you the length of a degree on the stalk of the new instrument. The more you multiply these fixed points, the more you insure the precision of the thermometer. When you have taken a certain number of points, you measure the remainder with the compasses. * * * * * +-----------------------------------+------------------------+ |Height of the Barometer in Inches. | | +-----------------+-----------------+ Correction in | |When the boiling |When the boiling | 1000ths of the | | point is found | point is found | interval between | | by immersing | by immersing | the freezing | | the Instrument | the Instrument | and boiling points | | in _Steam_. | in _Water_. | of Water. | +-----------------+-----------------+------------------------+ | ... | 30.60 | 10 } | | ... | 30.50 | 9 } | | 30.71 | 30.41 | 8 } | | 30.50 | 30.29 | 7 } | | 30.48 | 30.18 | 6 } | | 30.37 | 30.07 | 5 } Lower. | | 30.25 | 30.95 | 4 } | | 30.14 | 30.84 | 3 } | | 30.03 | 30.73 | 2 } | | 29.91 | 30.61 | 1 } | | 29.80 | 30.50 | 0 } | | | | | | 29.69 | 29.39 | 1 } | | 29.58 | 29.28 | 2 } | | 29.47 | 29.17 | 3 } | | 29.36 | 29.06 | 4 } | | 29.25 | 28.95 | 5 } Higher. | | 29.14 | 28.84 | 6 } | | 29.03 | 28.73 | 7 } | | 28.92 | 28.62 | 8 } |