130 Agricultural Jou/rnal of Victoria. 



historic times made ice by placing water in shallow earthen vessels, 

 covered with stalks of corn or sugarcane, and allowed nature to do 

 the rest. This system of refrigeration by means of the free and 

 rapid evaporation of water through porous vessels appears to have 

 been in use also in the palmy days of ancient Greece, and evidence 

 exists too of its practice in the middle of the third century, B.C. 

 Refrigeration seems to have been virtually ignored in very hot 

 countries up till recently, although in Greece and Rome, in Caesar's 

 time, it was so commonly adopted, that the serving of uncooled drink 

 to a guest was deemed the height of inhospitality. Apparently, the 

 practice of cooling liquors at the tables of the great was not in vogue 

 in France till the end of the sixteenth century, but by the end of the 

 seventeenth the luxury must have been very common, as the govern- 

 ment assumed control of the trade in ice and snow, and farmed the 

 business out, to raise funds for the support of an extravagant court. 

 As an article of commerce, however, natural ice did not assume large 

 dimensions till the nineteenth century, America and Norway being the 

 chief sources of supply. So extensive did the trade become in 188G 

 that a new impetus was given to shipbuilding, and the demand for 

 material in which to pack the ice became so great, that old neglected 

 sawmills were sought out, and high prices given for previous accumu- 

 lations of sawdust, the total year's supply harvested at that period 

 exceeding 20 million tons. The United States now easily leads the 

 rest of the world in the use of natural ice. It was not until 1845 that 

 ice began to be sold in London for general household purposes, al- 

 though considerable quantities were imported from Norway and 

 America prior to 1825, chiefly for the use of London confectioners. 



Artificial Refrigeration. 



The refrigerating properties of saltpetre were first practically 

 employed by the Italians, and about the year 1550 all the water, as 

 well as the wine, drunk at the tables of the Roman aristocracy, was 

 cooled by placing the liquor in a bottle or globular vessel immersed in 

 another wider one filled with cold water, saltpetre was then thrown 

 gradually into the water in the outer vessel, and dissolved. As far 

 back as 1507 various cooling mediums were used, the most common 

 being a mixture of salt and ice, which was employed by E'ahrenheit, in 

 1762, when he placed the freezing point of water at 82 degrees. 

 About the middle of the eighteenth century, scientists were experi- 

 menting with a view to the production of ice by mechanical means, 

 and, in 1755, Doctor William Cullen invented a machine which 

 reduced the atmospheric pressure with an air pump, and increased 

 the evaporation of water to such an extent as to produce intense 

 refrigeration and ice. This was the pioneer ice machine of any descrip- 

 tion. Some years later it was discovered that sulphuric acid had a 

 great affinity for water, and ice was made through this agency. 

 Early in the nineteenth century, Michael Faraday, assisted by Hum- 

 j)hrey Davey, demonstrated that gases could be liquified by mechanical 

 compressors, with continuous cooling apparatus to carry away the 



