ON INSTRUMENTS FROM ITALY. 127 



Luigi Antinori. The observations used to be taken at Florence, at 

 the Palazzo Pitti and at the Boboli Gardens, and in the Convento 

 degli Angeli ; and as far back as the year 1654 they were regularly 

 established at Vallombrosa, Cutigliano, Bologna, Parma, Milan, War- 

 saw, and Innsbruck. Observations were usually made at different 

 hours of the day, of the state of the thermometers exposed to the 

 north and to the south, the state of the sky, and the direction of the 

 wind. From a manuscript of Viviani, however, we learn that in 

 some places were noted the date, the hour, the temperature, the state 

 of the barometer, the wind, the sky, and the humidity of the air. In this 

 volume, entitled " Archivio Metereologico Ccntrale Italiano," you will 

 see registered the observations of those days, and besides others made 

 in this century. Now if the observations taken so long ago be 

 compared to recent ones, it will be seen that after the due corrections 

 have been made, or if observations be taken now with some of the 

 best instruments of the Accademia del Cimento, the meteorological 

 conditions of Tuscany have not changed. 



Passing on to the subject of hygrometers, besides the one imagined 

 by the great Leonardo da Vinci, and which is founded on the increase 

 in the weight of certain substances through the action of moisture, 

 others were used in which lengthening out or contraction of a given 

 substance served to determine the humidity of the atmosphere in 

 which it happened to be situated. Torricelli had already used oats. 

 In 1664, Dr. Folli da Poppi constructed a new hygrometer founded on 

 the expansion of paper with the variation of moisture, which, having 

 been perfected by the Accademia del Cimento, was reduced to the 

 shape in which you see it now. The movement of the hand to the 

 right or to the left, according as the paper expanded or contracted, 

 pointed out on the quadrant the relative quantity of moisture. Most 

 interesting likewise is this other one, which has been called the 

 condensing hygrometer. We owe it to the Grand Duke Ferdinand II. 

 It consists of a truncated cone made of a tinned sheet of iron, 

 covered on the inside with a layer of cork, and is supported on 

 a tripod. Below the smaller aperture, turned downwards, there is 

 suspended a hollow glass cone ending in a closed point, likewise 

 turned downwards, and provided towards the upper portion with an 

 escape-pipe. The superior cone is then filled with snow or ice, which 



