308 EIGHTH REPORT 1838. 



the Bihliotheqiie Universelle for June and July, 1838, by Profes- 

 sor Bonsdorf of Helsingfors. In this the author studies in ge- 

 neral the action of various metals on air and water, under the 

 following conditions : — 



1st. In air perfectly dry and free from carbonic acid. 



2nd. In air saturated with vapour of water, but free from 

 cai'bonic acid. 



3rd. In air containing both the latter. 



4th. In contact with liquid water and air, both free from, and 

 also containing carbonic acid. 

 He states that in the first condition no metal oxidates but po- 

 tassium and sodium. That in the second case no metal oxidates 

 but arsenic and lead ; in particular, that zinc, iron, and bismuth 

 do not oxidate, and that a gentle heat increases the action on 

 the first two. The author also brings forward some new views 

 on the subject of the deposit of moisture on metallic surfaces in 

 certain conditions, which, however, do not seem quite correct. 



7th. Experiments would also be desirable as to whether mag- 

 netism affects the rate or form of corrosion of iron, and hence, 

 whether position as to meridian has any thing to do with the 

 durability of engineering works in iron. 



8tli. Experiments vipon the suitability of various protecting 

 paints and varnishes, and the modes of their application to works 

 exposed to air and moisture, would be verj^ vahiable, giving pre- 

 ference to those which, with other obvious properties, dry soon- 

 est after rain, and, imder given circumstances, cause the least 

 deposit of dew. Upon this point Bonsdorf 's paper above alluded 

 to may be consulted. 



9th. A comparative set of experiments would be useful also 

 showing, under like circumstances, the effect of corrosion of sea 

 water, and of its mechanical abrasion by this fluid in motion, or 

 of the difference of action on iron in still sea water and in a tide- 

 way. 



10th. It would be exceedingly important also, as an element 

 of this investigation, as well as useful to the mechanic, to obtain 

 a correct measvu-e of the resistance to abrasion of various makes 

 of iron. This has been attempted by Mr. Fairbairn, unsuccess- 

 fully, by means of grinding on a stone a piece of weighed iron, 

 of given surface and under a given pressure, for a known time, 

 and noting the loss of weight. The most likely means of ar- 

 riving at this will probably be by making wheels of the various 

 irons to be tried, turned on the face and fitted on to steel axles, 

 suspending these in a swinging frame, and causing them to re- 

 volve for a length of time against the faces of other turned 

 wheels, all of one sort of iron, say tyred with No. 1 Welsh bar 



