Which area had its border set at the 49th parallel by president polk and britain in 1849?

Which battle was one of the most devastating for

Ascientist performs an experiment where she measures the mass of a piece of metal, pours acid onto the metal, washes the metal, and then re-measures the mass of the metal. the scientist repeats the experiment several times, each time increasing the amount of acid used. the dependent variable in the experiment is the: initial mass of the metal final mass of the metal amount of acid used washing the metal

What deadly disease cost many workers their lives before dr. william gorgas found a treatment?