198 Mr Johnston''s Visit to Benselius. 



poses of really refined analy^s. On a brick hearth raised 

 three feet from the floor, and covered at the height of three 

 or four more for the purpose of carrying off the fumes, stands 

 a small sand bath heated by a charcoal fire, and a little iron 

 fiimace with perforations for tubes, muffles, &c. These are 

 all he will see in the shape of furnaces ; but if an experiment 

 be in process, he will probably notice upon this hearth a neat 

 arrangement of bottles and tubes, stimulated to action in their 

 inward parts by the heat of a large spirit lamp, such as the 

 coffee-drinkers of Paris use for boiling their morning be- 

 verage. 



But before this time he has been looking to the left, where 

 the view opens through a doorless doorway into the second 

 chamber, and his eyes have rested on a glass-casfe standing 

 upon the table right before him. He may walk forward and 

 examine it. It is the balance. How much light has that little 

 machine scattered over every department of nature ! how many 

 phenomena has it explained ! how many hidden truths has it 

 made known ! how many disputes too has it settled, — how 

 many hypotheses overthrown, — how much ingenuity scattered 

 to the winds. Who in former times could have imagined that 

 the determination of abstract truth and the developement of 

 the laws of nature woidd ever come to be referred to the os- 

 cillations of those two unstable arms ? But regard that balance 

 with earnest attention, for it has wrought mighty service in 

 the cause of science. That mode of raising up and resting 

 the arms and scales, is a contrivance of the late Assessor Gahn, 

 whose ingenuity in these matters has been so justly praised. 

 The merit of first making the scales loose, and resting them 

 on knife edges, — an invention which Berzelius praises much, 

 without knowing to whom to attribute it, is due to the cele- 

 brated Mr Cavendish. His balance, which came into the pos- 

 session of Sir Humphrey Davy, and by him was given to Mr 

 Children, is fitted up in this way ; yet no one thought it of any 

 consequence till Mr Robertson of Devonshire Street, Portland 

 Place, saw the merit of it, and by adopting it, has brought his 

 balances to that high degree of perfection for which they are so 

 highly esteemed by those who are fortunate enough to possess 

 them. Mark one other thing in that balance which lessens 



