During these journeys he discovered the connection between the Amazon and Orinoco river systems and surmised that altitude sickness was caused by lack of oxygen. 旅程中他发现亚马逊河系与奥利诺科河系是相通的，并推测高山病起因于缺氧。
For many, approaching Tibet gradually by train will be preferable to flying in, as it will allow more time to acclimatise and reduce the chance of altitude sickness. 更好的是，与坐飞机相比，乘火车将是逐渐的抵达西藏，这样将使乘客有更多的适应时间和降低发生高山病的几率。
