74 ON A NEW FORM OF ACTINOMETER. 
Now, while this steam-engine is giving one motion to the pen, 
the clock-work is giving it another motion over the paper with its 
or compound of the two motions. 
You will see, then, how this machine will show not only the 
hours when the sun shines, but also the intensity of that heat. In 
such an arrangement some of the water evaporated must be lost in 
e machine, and I propose to measure the water into the reser- 
voir in the morning and measure it out at night, so determining 
exactly the quantity of water boiled away during the day, and by 
means of the pen record the relative rate of evaporation during each 
moment of sunshine. Experience will no doubt suggest precau- 
tio modifications of this proposal which will make it a 
complete machine. 
