Theories and Experiments 203 



compressed in a vacuum to sink in water; for I have several times 

 placed in a vacuum pieces of lungs and whole lungs, and they 

 remained extremely inflated while in the vacuum; but as soon as air 

 was admitted to the receiver, they became flat and red and sank 

 when placed in water. (P. 150.) 



Finally, before leaving this fruitful epoch, I think I should 

 reproduce here a very curious plan of experiments suggested to 

 the English physicist Beale ;| by his celebrated compatriot Boyle: 



It would be, I think, very important to see the effects produced 

 on plants placed in Mr. Boyle's air-pump, and likewise on cherry- 

 blossoms, etc. 



The distinguished Mr. Boyle suggests that in the approaching 

 season I should see: 



1. Whether seeds germinate in the vacuum receiver; 



2. Whether lack of air is harmful to sensitive plants; 



3. Whether grafting pear buds on spina cervina (the only vege- 

 table purgative known in England) will give the pears purgative 

 qualities. 



4. Whether the eggs of silkworms will hatch in the receiver when 

 the season has arrived. 



I should, besides, investigate whether aquatic plants live in water 

 from which the air has been removed by the pump .... 



One of these experiments was carried out on lettuce seeds. Those 

 which had been planted in open air measured IV2 inches in height 

 after a week, the others had not sprouted; but they germinated when 

 air was admitted. 



We shall not dwell longer on these attempts which, as we have 

 noted, relate almost exclusively to the effect of an almost complete 

 vacuum. Except for a few experiments of Boyle and Musschen- 

 broek, air that is merely rarified is, in fact, not considered in them 

 at all. 



And yet, as we have seen, these physicists tried to find in these 

 experiments explanations for the physiological disturbances ex- 

 perienced by travellers who ascend high mountains. This interest 

 is shown also in a curious passage in the History 10 of the Academy 

 of Sciences for 1705; it shows at the same time how many uncer- 

 tainties then assailed the minds of the physicists themselves on the 

 question of measuring altitudes by the barometer: 



There is some reason to believe that the air expanded in a tube 

 is not quite of the same nature as air at the top of a mountain. If 

 one puts lukewarm water in the vacuum machine, it boils very hard 

 as soon as half of the air has been pumped out, because that which 

 was naturally mixed with this water, and which had already been 

 warmed a little, when it is freed of half the weight which pressed 



