840
��SCIENCEi
��[Vol. v., Vo. 11«.
��The quaotity of alknli required to saponify the fat is another valuable means of judging of the purity of a butter. This equivalent is an abstract number obtained by dividing the molecular weight of the alkali employed by the number of milligrams of it used in saponi- fying a given weight of the fat. Butter-fat contains acids (butyric chiefly) which have a lower molecular weight than oleic, margaric, and palmic acids. The saturation equivalent of a butter-fat is tlierefore expressed hy a smaller number than if it were composed solely of glycerides of the acids with a bigher molec- ular weight. The determiuation of the equiv- alent being an easy one, it is generally made as the first test in determining the genuineness of a butter sample. For genuine butters, this number is about 245. When it goes above •250, the samples should be regarded with sus- picion. In oue case of a Jersey butter very rich in butyric acid, thia number fell to 239.8, On the other hand, in four samples of tallow, lard, and oleomargarine (two), the numbers were 280, 284. 282, and 281 respectively.
Pure butler contains a certain proportion of glycerides of fat acids soluble in water (butyric, capronic, caprylJc, etc.). The percentage of these acids to the total weight of butter-fat is about five. In thirty analyses the lowest percentage found was 4.49, and the highest (except in one case) 6.66. In the case of the Jersey cow's butter, already mentioned, this number was 6.79. Tallow and lard have at most only a trace of these acids. In commer- cial oleomargarines the highest jiercentage found was .5G, and the lowest .20. The deter- mination of the soluble acid requires much time ; but it is not a difficult operation, and it is the most certain method of determining the purity of a butter. A sample which would give no more than four per cent soluble ncid would be open to condemnation. It would either be a very poor sample of genuine butter or else an adulterated article.
Pure butler which has not been melted gives, with polarizetl light and a selentte pintc, a pure unifoi'm tint of red or blue to the field of vision. Adulterated butter in similar circum- stances always gives a mottled appearance to the field. This ia a very simple and speedy qualitative teat for the purity of butter, but is not sufficient in itself to definitely determine the matter.
The difflculties which make the analyses of mUks of little practical value are equally as great with butter. A more extensive study of their composition, however, is certain to lead to profitable results. PI. W. Wiley.
���THE SASKATCHEWAN COUNTRY.
The district at present attmcling attenttuo aa the scene of an insurrection of half-brecda and Indians against the Canadian government is situated on the North Saskatchewan River, near the northern margin of the great plains. The vast region of plain and prairie, which occupies the whole central i»rtion of the con- tinent, crosses the 4!)th parallel of latitude — which constitutes the international boundary- line — with a width of 750 miles, but extends north of the boundaiy about 300 miles only, being there limited by the edge of the great northern forest which stretches, with little in- terruption, to beyond the arctic circle. Prai* ries of considerable size occur, it is true, in the valley of the Peace, but these are isolated from the great plains by wide forests. There is reason to believe that the greater part of the prairie country in Canadian territorj' might become permanently wooded but for the almost annually recurring prairie-fires, which are still tending to increase its area. The soutbera edge of the forest is, however, in the main, coincident with that of a region of abundant rainfall.
The northern border of the prairie country may be generally defined by a line drawn fiom the vicinity of the city of Winnipeg westwanJ to the junction of the Assiniboine and Qa'- Appelle rivers ; thence north-westward to the junction of the North and South Saskatche- wan riiera ; tbence westward, nearly following the latter river, to Edmonton ; from that point south-westward to Calgary, on the Bow ; and thence southward along the eastern base of the Rocky Mountains. The total area Uidb outlined, which is either altogether treeless or characterized by wide stretches of prairie in- ters|>ersed with scattered groves of aspen and other trees, is approximately 300,000 square miles. The southern and south- western parts of this region may be described as enUrety without wood, though even there the rivers are almost invariably Mnged by groves of Cot- tonwood.
The general elevation of the plains of the Canarlian north-west is very considerably less than that of the corresponding portion of the continent farther south, the mean height of the whole region above outlined being probably less than two thousand feet above the sea-level. The most pronounced inclination, however, giving direction to the rivers of this portion of the great plains, is that from the base of the Rocky Mountains to the east or north-east. The Red-River valley, which constitutes t
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