Comparison of the imperial and US customary measurement systems metre, as 1852 metres. Traditionally, both Britain and the US used three different weight systems: troy weight for precious metals, avoirdupois weight for most other purposes and apothecaries' weight for medicines. However, apothecaries' weight has now been superseded by the metric system. One important difference is the widespread use in Britain of the stone of 14 pounds () for body weight. This unit is not used in the United States, although its influence was seen in the practice, until World War II, of selling flour by a barrel of 196 pounds (14 stone). Another difference arose when Britain abolished the
Heavy metals adverse biological effects). An average 70 kg human body is about 0.01% heavy metals (~7 g, equivalent to the weight of two dried peas, with iron at 4 g, zinc at 2.5 g, and lead at 0.12 g comprising the three main constituents), 2% light metals (~1.4 kg, the weight of a bottle of wine) and nearly 98% nonmetals (mostly water). A few non-essential heavy metals have been observed to have biological effects. Gallium, germanium (a metalloid), indium, and most lanthanides can stimulate metabolism, and titanium promotes growth in plants (though it is not always considered a heavy metal). Heavy