Page:Popular Science Monthly Volume 38.djvu/688

670 strength. The statement of Prof. Griffin that Milwaukee cement has been shown to have the greatest crushing strength is rather too sweeping, to say the least, as all first-class Portland cements are superior to Milwaukee in this respect, and there are a number of brands of American natural cements that are in every way its equal. Although English Portland cements are among the best in the market, still they are equaled by both German and French Portland, while there are now manufactured in the United States Portland cements that in tensile strength exceed any imported cements. Briquettes made of American Portland have shown a tensile strength of eleven hundred pounds at the end of twenty-six weeks.

A careful study of the diagrams will give a correct idea of the relative values of typical English and American Portland cements, American natural cements, and Portland and natural cements. It is not intended to show in Fig. 2 that Milwaukee cement is inferior to all American natural cements, but simply that there are American natural cements that under the same treatment will give at least as good results. The numbers along the bottom of the diagrams indicate the age of the briquettes in weeks; the numbers at the side indicate pounds.



THE object of the acclimatation of animals and plants is to add to the species, races, and varieties of a country species, races, and varieties of other countries that may be useful or simply agreeable to it, whether they be represented in the wild or the domesticated state. The history of the subject is not complicated. It is a general fact that the sciences which we now have to study before entering into the practice of the arts originated after considerable applications of them had been made. They cultivated wheat long before agronomical institutes were founded; iron was extracted from its ores before metallurgy was known; we took care of the sick—and some pretend that we cured them—before the science of medicine existed. So we domesticated wild animals and took them from country to country, from climate to climate, before we had a science of acclimatization to direct us. But while most of the sciences originated in the distant past, the science of acclimatization is new. Something is indeed said on the subject in the books of Buffon, Bernardin de Saint-Pierre,