Progress of Invention. 63 



the 42°. It requires 15° to 16° (about 60° to 61° F.) of 

 summer heat to live, and 18° to mature its fruits. The lowest 

 temperature it can withstand is — 1° (30'2° ¥.), and the mean 

 annual temperature must be about 4-9*5°. Such at least must 

 have been the Greenland climate at its lowest limit, for the 

 Daphnogene, the MacClintockia, and the Zamites, probably 

 required a higher temperature. The present mean of this 

 country being — 6*3° (20* 75° ¥.), it, must during the miocene 

 epoch have been 16 centigrade degrees warmer. 



PROGKESS OF INVENTION. 



Formation of Crystals. — There can be no doubt that time is 

 often an essential element in the formation of crystals ; this is 

 particularly true of the diamond and other precious stones, and no 

 doubt constitutes the obstacle to their artificial production. 

 Hitherto, the chemist has been unable to crystallize certain com- 

 pounds thrown down from their solutions ; a simple means of 

 effecting this has, however, been devised by M. Frenny. He con- 

 sidered that the amorphous form of precipitates arises from the 

 rapidity with which the precipitation takes place, and therefore 

 expected to obtain crystals by diminishing that rapidity. The 

 result was such as he anticipated. In this way he procured crystals 

 of the sulphates of baryta, strontia, and lead, of the carbonates of 

 baryta and lead, etc. He obtained even crystals of quartz, which 

 were sufficiently hard to scratch glass ; but they were not pure, 

 containing five per cent, soda and twenty-seven per cent, water. 



Simple forms of Galvanic Battery. — Hitherto the metallic 

 solution produced in the galvanic battery, when saturated, was no 

 longer capable of use for the purpose. It has been found, however, 

 by M. Montiers, that such need not be the case, if we avail our- 

 selves, in succession, of two metals having very different electro- 

 chemical properties. As an illustration of this principle, he first 

 places a cylinder of malleable or cast-iron in a vessel, and inside 

 of the iron a prism of carbon ; then pours in dilute sulphuric acid. 

 The iron and graphite act as electrodes, and the electricity deve- 

 loped by a single couple of this kind is sufficient to keep a bell- 

 ringing apparatus in action for a considerable time. When this 

 battery is exhausted, he concentrates the solution of sulphate of 

 protoxide of iron formed by it, and immerses in it electrodes, 

 which in this case consist of zinc and carbon. The zinc is dissolved, 

 hydrogen is liberated, and hydrated protoxide of iron is set free. 

 The energy of this latter battery is sufficient to keep the bell-ringing 

 apparatus in action for several months. M. Montiers also avails 

 himself of the fact that oxide of zinc acts as a base with acids, but 

 as an acid with ammonia and other strong bases, for the production 

 of a very economical battery. For this purpose, he avails himself 



