the fruitless attempt of some miners in searching for coal, in Cromarty, by boring, 

 states that they found a true artesian well, which put a stop to their labours ; 

 and although the waters were not strongly tinctured with ferruginous matter, yet 

 he could see every pebble and stalk over which the water passed, enveloped with a 

 ferruginous coagulum. I can easily conceive that, before the carboniferous era, 

 the atmosphere, surcharged with carbonic acid, supplied the early seas with a 

 sufficient abundance of that gas to hold in solution the iron, lime, magnesia, kc. ; 

 that the latterelements were partially used upby the fish, with which those early seas 

 abounded, and as the purification of our atmosphere proceeded, the iron, parting 

 with its double dose of carbonic acid, gradually departed, giving to the formation 

 its peculiar red tinge, by which it has acquired its name, the Old Red sandstone. 



Thus whilst it ia interesting and useful to trace (if possible) the source of such 

 combination of elements as the peroxide of iron, there are often other considera- 

 tions arising out of the investigation, of equal importance to the student of natural 

 philosophy. Herefordshire, for instance, has been proverbial for the salubrity 

 of its atmosphere, and the freedom of its inhabitants from those epidemic scourges 

 which have so often depopulated districts resting upon other geological formations ; 

 and it is a remarkable fact that, in the two visitations of cholera, not one case 

 occurred in the county. Now, it becomes an interesting question — Is there any- 

 thing peculiar to the Old Red sandstone, which would in any way contribute to 

 this exception ? The faculty have long been accustomed to consider that cholera 

 follows the track of typhus, and that typhus is often occasioned by gaseous emana- 

 tions arising from the decomposition of animal and vegetable matter ; but in 

 what way such effects are produced, science has not as yet been able to determine. 

 Whether by producing a change in the electrical state of the atmosphere it 

 induces disease (Sir James Murray), or by being taken into the lungs, it produces 

 a peculiar chemical change in the constitutents of the blood, thereby inducing 

 morbid action. During the progress of some chemical investigations upon the 

 properties of sewage water from thickly inhabited places in this county, I was 

 surprised to find that its composition varied materially from that stated by other 

 analysts in other localities ; and I was led to inquire whether there was any 

 peculiar property possessed by the soil of the district which would account for the 

 difference. Knowing the composition of the soils, and the quantity of ferruginous 

 matter they contained, and being aware that when solutions of any salt of iron were 

 placed in contact with sewage, the whole of the iron would be precipitated as an 

 insoluble sulphuret, it remained then to be proved whether the finely divided 

 peroxide of iron would act analogously to the solutions of its salts, which, indeed, 

 by direct experiments, I found to be the case ; and the play of affinities were as 

 follows — the sulphur of the sulphuretted hydrogen, combined with the iron of the 

 peroxide, forming the metallic sulphuret ; the liberated hydrogen combining with 

 the liberated oxygen of the peroxide, forming water ; thus the most deadly 

 compound gas, by transposition of its elements with peroxide, was converted into 

 two most innocuous compounds, water and the sulphuret of iron, and the sulphuret 

 again, by exposure to the atmosphere, became re-converted into the peroxide of 

 iron, vnth liberation of sulphur, not again to be converted into the deadly 

 sulphuretted hydrogen, but into the useful sulphuric acid. From the above con- 



