Midland ScientiJiG Association. 379 



atmosphere of hydrogen retain on cooling a portion of that gas so 

 obstinately that mere exposure in vacuo will not liberate it, but the 

 separation may be effected by heat. In such a case the force holding 

 the molecules of gas and metal together differs essentially from co- 

 hesion. Mr. G-raham also found that Platinum and Palladium absorb 

 hydrogen in a high degree ; Palladium taking up 963 times its own 

 volume. The Palladium is then found to have the properties of an 

 alloy, confirming the belief in the metallic nature of hydrogen. 

 This power of occlusion, as it is called, of a gas by a metal is also 

 seen in the case of iron, which condenses both hydrogen and carbonic 

 oxide. Mr. Brown then stated that he had discovered by experiment 

 that metallic coj)per possesses a somewhat similar property. In this 

 case the gas most readily absorbed, being carbonic, it is occluded at 

 ordinary temperatures, and cannot be due to the formation of an 

 alloy. The copper used was exposed in the form of a thin, clean, 

 spiral ribbon, in a glass tube, in an atmosphere of perfectly dry 

 carbonic acid, which has no chemical action upon copper. After a 

 while a vacuum was made in the tube by means of Sprengel's 

 mercurial pump. Heat was applied, the gases evolved measured 

 and analysed ; the whole of the absorbed gas was evolved at a tem- 

 perature a little above 100° C. The amounts absorbed were varia- 

 ble, the largest amount being about 3-10 of the bulk of the copper 

 used. This absorption took place in 18 hours, at a temperatiare of 

 17° C When freshly reduced copper was exposed to the air but 

 for three or four minutes, traces of gas were given off on heating in 

 vacuo. It was found that copper reduced from the black oxide was 

 capable of occluding larger quantities of carbonic acid than the metal 

 in an ordinary state. In the experiments the total quantity evolved 

 was almost equal to the bulk of copper used ; rather more than 1-3 

 was evolved at a little over 100° C. ; at 600 C. a partial re-absorp- 

 tion took place, about 1-6 of the total volume evolved ; the whole 

 was evolved at about 1,000° C. Why part of the gas should thus 

 be given off at one temperature, and the remainder at another, and 

 why part should be re-absorbed, the author could not explain. He 

 considered the absorption of carbonic acid by copper to be a true 

 case of occlusion, and not one of surface cohesion only, nor can it 

 be chemical. Hydrogen and nitrogen were also found to be occluded 

 in small quantities. 



5. Mr. E. Brown read the last paper on " The Waste of Kock- 

 masses by Solution," pointing out that amongst the various subeerial 

 agencies by which the present surface of the country had been shaped, 

 the chemical solution of various beds, especially of Chalk and Lime- 

 stone, has been and still is one of the most active. He remarked 

 that the disappearance of the rainfall in the limestone district of 

 Derbyshire without the formation of streamlets proves that the 

 numerous fissures carrying the rain away are kept open by the 

 solution of their sides. The caverns at Castleton and Buxton are 

 undergromid rivers, and these channels are hom-ly increasing in size, 

 whilst the exposed cliffs are reduced by every shower. The quaintly 

 shaped stones used for artificial rock -work at Buxton are fragments 



