57° 



THE POPULAR SCIENCE MONTHLY. 



fercnce between the action of diffused day- 

 light sufficient to view pictures and of direct 

 sunlight is at least forty times as great, and 

 in summer probably four hundred times. 

 Hence a picture which would fade in ten 

 years in sunlight might be preserved for 

 something like twelve hundred years in a 

 yellow light. The acidity of drawing-paper 

 should be corrected by a wash of a dilute 

 solution of borax ; and in no case ought any 

 paste, gum, or glue, to be placed at the 

 back of a drawing for the purpose of mount- 

 ing it. 



The Mineral Springs of Europe. — Dr. J. 



Burney Yeo has made a classification of the 

 mineral springs of Europe into groups ac- 

 cording to the composition of their waters. 

 The first group includes the simple thermal 

 waters, or " indifferent " springs, the tem- 

 perature of which is above 80° Fahr. The 

 waters are chiefly used in baths, and, when 

 administered internally, it is simply for get- 

 ting the purifying solvent influence that 

 might be obtained from drinking pure hot 

 water. They are efficacious in chronic 

 rheumatism, chronic gouty inflammation of 

 the joints, sciatica and other forms of neu- 

 ralgia; hysterical and hypenesthetic states 

 of the nervous system ; old, painful wounds 

 and cicatrices, and cases of loss of muscular 

 power when not dependent on diseases of the 

 nervous centers. Some of the most popular 

 springs fall under the head of " common salt 

 waters." Their strength varies, and it is cus- 

 tomary to fortify them or dilute them, arti- 

 ficially, according as they may need. Used 

 in baths, they stimulate the peripheral ves- 

 sels and nerves, and promote capillary cir- 

 culation. They improve the tone and nutri- 

 tion of the skin, and indirectly stimulate 

 tissue-change. Internally they act as stimu- 

 lants and indirectly as tonics to the organs 

 of digestion and assimilation ; but in per- 

 sons with highly sensitive mucous mem- 

 branes they may cause irritation and dis- 

 comfort, especially if given in too large 

 doses. They are employed in baths in 

 cases of hypersensitiveness of the skin ; in 

 some forms of retarded convalescence from 

 acute disease ; in scrofulous and inflamma- 

 tory enlargement of joints ; and in chronic 

 hypertrophies of certain organs. Internally 

 they are beneficial in cases of atonic dys- 



pepsia and chronic gastric catarrh, and in 

 those low states of health which are often 

 contracted by prolonged residence in trop- 

 ical climates. The alkaline waters are char- 

 acterized by the presence of considerable 

 proportions of carbonate of soda and free 

 carbonic acid in varying amounts, and are 

 exemplified at Yichy. Some of them also 

 contain common salt, when they arc classed 

 as muriated alkaline waters, and some, of 

 both simple and muriated springs, are hot 

 and some cold. Many of the springs of this 

 class are found to be most valuable curative 

 agents. The waters are all taken internally, 

 and are used in baths, but not very largely. 

 They are applicable to the treatment of a 

 great number of chronic maladies. In mod- 

 erate doses they are solvent and purifying, 

 correct acidity, promote tissue-change, and 

 possess active diuretic properties. If taken 

 too largely, they depress the heart's action 

 and cause emaciation. They are given in 

 cases of acid dyspepsia ; in gouty constitu- 

 tions ; in cases of renal calculous disorders 

 and gravel ; in diabetes ; and in cases of 

 torpid liver, with tendency to gall-stones, 

 in constitutions which would not bear the 

 stronger aperient waters. They are of serv- 

 ice in the treatment of chronic catarrh of 

 the bronchial and other mucous membranes. 

 The waters containing common salt are more 

 tonic and stimulating than the simple alka- 

 line waters. The group of the sulphated 

 waters includes all the best-known aperient 

 waters, which owe their peculiar qualities to 

 the presence of soda and magnesia, singly 

 or combined. Some of the springs contain 

 also carbonate of soda and chloride of so- 

 dium, which add greatly to their remedial 

 value. This has led to the subdivision of 

 the group into the simple sulphated or bit- 

 ter waters — Friedriehshall, Pullna, and Hun- 

 yadi — and alkaline sulphated waters — ex- 

 emplified in Carlsbad, Maricnbad, Franzens- 

 bad, and Tarasp. The iron or chalybeate 

 waters are the tonic waters. They arc valu- 

 able in proportion to their purity — that is, 

 to the absence of other solid ingredients — 

 and in proportion, usually, to the amount 

 of free carbonic acid that they contain. A 

 sixth group comprises the numerous and 

 well-known sulphur-springs, both hot and 

 cold, which are freely used for baths. The 

 celebrated Pyrenean spas are nearly all hot 



