140 PHYSICAL SCIENCE BK. in 



the foam is solidified. It is necessarily light, being 

 formed by concretions of windy, empty material. 



9 There are other peculiarities attaching to waters 

 of different kinds, of which no explanation can be 

 offered. For example, why should Nile water make 

 women more fruitful ? So effective is it in this 

 respect that in some instances wombs shut up in 

 prolonged barrenness have relaxed so as to render 

 conception possible. Or why should certain waters 

 in Lycia prevent miscarriage, being sought after by 

 ladies who are subject to this frailty ? For my own 

 part I set these down among vulgar errors. It is 

 firmly believed by people that certain waters, whether 

 applied outwardly or taken inwardly, affect the body 

 with scab, certain with leprosy and foul blotches 

 over the skin. Water gathered from dew, they say, 



10 has this fault. Wouldn t any one suppose that water 

 that turns into ice is the heaviest of all ? The 

 truth is just the opposite of this. The change takes 

 place in the thinnest water, which for that very 

 reason is most easily congealed by the cold. The 

 origin of the stone that resembles ice is plain from 

 the very name used for it by the Greeks. They apply 

 the term crystal (/cpva-raXXo?) equally to the transparent 

 stone and to the ice from which the stone is supposed 

 to be formed. Rain water, which contains very little 

 solid matter, once it is frozen becomes more and 

 more condensed through the persistence of the longer 

 cold until all the air is expelled, and it is compressed 

 to the last degree ; then what was once moisture is 

 changed into stone. 



