Before agar, microbiologists had experimented with other foodstuffs as microbial media. They turned to substances rich in the starches, proteins, sugars, fats, and minerals that organisms need for growth, testing with broths, bread, potatoes, polenta, egg whites, coagulated blood serums, and gelatine. However, none worked particularly well: all were easily broken down by heat and microbial enzymes, and their surface, once colonized, became mushy and unsuitable for isolating microbes.
• “Archaeologists Say They’ve Identified Traces of a 2,000-Year-Old Love Note Still Etched Into a Wall in Ancient Pompeii.” (Smithsonian).
，更多细节参见一键获取谷歌浏览器下载
With a thousand points, you barely notice the delay. With a million, you're doing a million distance calculations for every single query. On a phone updating the map as the user scrolls, that's untenable.
* 获取数字的第digit位（从右往左，0表示个位）