ON INSTRUMENTS FROM ITAL Y. 12; 



increased, Here are two tubes which Torricelli used in his firct 

 experiments. 



Before speaking of the Accademia del Cimento, it will not be out of 

 place if I allude here to certain measuring instruments, which were 

 made use of in its researches, and which are to be found described in 

 the " Libro de Saggi " as belonging to the academy ; but some of 

 which, however, were made before its foundation, according to the 

 directions chiefly of the Grand Duke Ferdinand II. And beginning 

 with thermometers, it is useful to notice how even Galileo had sub- 

 stituted wine for water, which by freezing easily broke the thermo- 

 metrical bulb ; while the Grand Duke had replaced wine, first of all by 

 coloured alcohol; and afterwards, in order that the deposit thrown 

 down by the colouring matter on the inside of the bulb should not render 

 the reading less clear, he substituted natural alcohol ; which they call 

 " acquarzente." Here is a series of thermometers of that period. But 

 I must tell you that I have only brought to London a very small part 

 of the ancient instruments existing in Florence. This is the thermo- 

 meter, which we owe to the Grand Duke, it is called the " cinquanti- 

 grado," because it was divided into fifty parts in a masterly manner by 

 means of these little grains of enamel or glass ; and it is exceedingly 

 interesting to observe how the thermomelrical bulb was constructed, 

 not merely in a spherical shape, but even in the cylindrical one which 

 has now come into generalise ; as you may see in this second thermo- 

 meter, which is also a " cinquantigrado." As to the way of dividing 

 them into degrees, this is the method they employed : They immerged 

 the thermometer, just as we do, into melting ice or snow, and they 

 marked the point to which the alcohol .descended which in 

 thermometers of 50 was about I3'5 ; while they remarked that the 

 greatest cold of Florence could reduce it on some occasions even to 7* 

 Then they exposed it to the rays of the sun at midsummer, in the open 

 air, without any object of reflection whatever ; in this case the 

 " cinquantigrado " rose, in Florence, to 43 at the highest, and in the 

 shade, at the same season, to 34 ; so that the difference between 

 melting ice and the extreme heat was divided into 30 ; and these were 

 the points of comparison for their thermometers. Other thermometers, 

 were then constructed with arbitrary scales of 60, 70, 100, 200, or evea 



