POPULAR MISCELLANY. 



573 



with the products of their labors, by filtra- 

 tion. Assisted precipitation is employed to 

 remove suspended matters in very fine par- 

 ticles, the dissolved salts which make water 

 hard, and coloring matters, especially the 

 peaty substances that produce a dark -yellow 

 stain. Sulphate of aluminum, or the ammo- 

 nium aluminum sulphate, which is common 

 alum, has been found to be the best precipi- 

 tant for the suspended substances, forming 

 with them an insoluble coagulum. One grain 

 of alum to the gallon is ordinarily sufficient, 

 and this has no deleterious effect on the 

 water. The insoluble clot which it forms 

 carries down with it the products of putres- 

 cent decomposition which are present, and 

 the microbes, or so-called disease -germs. 

 For softening hard water, the precipitant 

 used is lime, the lime carbonate thrown 

 down being removed by filtration. The only 

 material yet found to be available for fil- 

 tration on a large scale is fine sand. In or- 

 der to avoid the expense of the system of 

 sand filtration, which has long been em- 

 ployed in England, a mechanical contrivance, 

 called the National Filter, has been devised 

 in this country. The filter consists of a 

 closed tank, two thirds full of sand. The 

 water enters at the top of the tank, filters 

 downward, and escapes by a perforated pipe 

 at the bottom. To clean the filter, a reverse 

 current is sent in by a perforated pipe lying 

 about a foot below the surface of the sand, 

 most of the dirt being deposited in the up- 

 per six inches, and the water, after taking 

 up the impurities, escapes by an outlet at 

 the top. A reverse current is then sent 

 through the sand by the perforated pipe at 

 the bottom. Every portion of the bed is 

 floated loose, and by the attrition of the 

 grains of sand upon one another the impu- 

 rities are scrubbed off ; they are then floated 

 to the top, and carried away. When the 

 cleansing is complete, the reverse current is 

 shut off, and the sand settles down into a 

 fresh, uniform filter-bed. 



The English Glacial Moraine.— Prof. H. 



Carvill Lewis's studies of the glacial termi- 

 nal moraine of England were based upon 

 the principle that every glacier, at the time 

 of its greatest extension, is bounded and 

 limited by a terminal moraine. The great 

 ice-sheet which once covered northern Eng- 



land was found to be composed of a number 

 of glaciers, each of which was bounded by 

 its own lateral and terminal moraines. These 

 glaciers were studied in detail, as the North 

 Sea glacier, the Wensleydale glacier, the 

 Stainmoor glacier, the Aise glacier, the Irish 

 Sea glacier, the separate Welsh glaciers, each 

 of which was found to be distinguished by 

 characteristic bowlders, and to be defined by 

 a well-marked moraine. The great terminal 

 moraine of the united glaciers of England is 

 a very sinuous line, five hundred and fifty 

 miles in length, extending from the mouth 

 of the Humber to the farthest extremity of 

 Carnarvonshire ; and, except where it sepa- 

 rates the Welsh glaciers from the North Sea 

 glacier, it everywhere marks the extreme 

 limit of glaciation in England. 



The "High-Altitude" Cure for Con- 

 snmption. — In contemplating the resort to a 

 high altitude for treatment of consumption, 

 which is now becoming common, it is well 

 to consider whether the constitution of the 

 patient is adapted to the conditions that he 

 will meet there. From the fact that the at- 

 mospheric rarefaction at elevated positions 

 throws a greatly increased strain upon the 

 circulatory apparatus, we have a right to 

 regard valvular disease of the heart or fee- 

 ble circulatory power as a strong contra- 

 indication against trying the high-altitude 

 treatment. For a similar reason that treat- 

 ment is inapplicable to persons of advanced 

 age, in whom the arteries are likely to have 

 undergone more or less of senile degener- 

 ation. As the rarefaction of the air in- 

 creases the number and depth of the respi- 

 rations and promotes the elimination of car- 

 bonic acid from the lungs, it is not adapted 

 to cases in which the lung-tissue has been 

 much destroyed. Although superficial effu- 

 sions of blood are sometimes suffered at 

 great heights, bleeding at the lungs has not 

 been observed there, and the danger of it is 

 not believed to be increased. The preva- 

 lence of cold at high altitudes is a fact to be 

 considered by persons whose sufferings are 

 increased by low temperatures. The combi- 

 nation of cold, dryness, and rarefaction con- 

 stitutes a climate of a highly stimulating 

 character. It is consequently exciting, and 

 unfavorable to nervous persons, while it may 

 be beneficial to the phlegmatic. The cases 



