ACTION OF RADIANT HEAT. 33 



3. Chalybeate or ferruginous : those in which iron is a leading con- 

 stituent ; and 



4. Sulphurous : those that contain sulphureted hydrogen. 

 Of the latter class there are two instances. 



Almost without exception the rest of the waters of this locality 

 possess some of the properties of those belonging to the first three 

 classes, being a combination of gaseous, saline, and ferruginous princi- 

 ples, their difference, as you will observe, being more one of quantity 

 than of quality. As a matter of convenience they are designated as 

 cathartic, alkaline, iron, and sulphur waters, according to the degree 

 in which these characteristics present themselves. 



Mineral waters were known at an early day, their use being held 

 in high repute by the ancient Greeks and Romans, as well as by their 

 less illustrious successors. Their physiological action and therapy are 

 not, however, perfectly understood. With the exception of the chalyb- 

 eate, the persistent use of the cathartic, alkaline, and sulphur waters fa- 

 vors retrograde metamorphic action, the ferruginous alone producing an 

 opposite effect and increasing the number of the red blood-corpuscles. 



From the diversified character of their constituents their applica- 

 tion as therapeutic agents must necessarily have a wide range. Prob- 

 ably the best results from their use are obtained in those functional 

 diseases that are connected with derangement of the portal circulation, 

 and in certain rheumatic and arthritic affections. In some fonns of 

 indigestion their use is attended by very gratifying results, as well as 

 in certain types of renal difficulties. In anaemia, uncomplicated with 

 organic lesions, the iron waters are of decided benefit. That many 

 persons injure themselves from the injudicious use of the waters is a 

 matter of common observation. They are medicinal, and should be so 

 regarded and used accordingly. The late Dr. Steele, in referring to 

 this subject, remarked that " there are numerous persons who flock 

 about the Springs during the drinking-season, without any knowledge 

 of the composition of the waters, and little or none of their effects, 

 who continue to dispose of their directions to the ignorant and unwa- 

 ry, with no other effect than to injure the reputation of the water and 

 destroy the prospects of the diseased." 



-*-**- 



ACTION OF RADIAXT HEAT OX GASEOUS MATTER. 



By Professor JOHN TYXDALL, F. E. S. 



r I IHE Royal Society has already done me the honor of publishing a 

 -*- long series of memoirs on the interaction of radiant heat and gas- 

 eous matter. These memoirs did not escape criticism. Distinguished 

 men, among whom the late Professor Magnus and the late Professor 



VOL. XIX. 3 



