Africa’s gem of a country

Enlightened rule: Botswana’s Seretse Khama with his wife Ruth and family nickel, copper, gold and uranium mines. Lucrative diamond exports have funded economic and social development, and the country also has many businessfriendly incentives and policies to build up a service sector economy.

Socially, the government is progressive and forward-thinking, as shown by the policy of providing free anti-retroviral treatment to combat hIV/AIDS.

The country spends 8 per cent of its GDP on education, one of the highest proportions in the world.

Botswana also benefits from tourism, being home to the Okavango Delta — a large, swampy inland area that is one of the world’s natural wonders, attracting vast herds of animals in the dry season.

Ellen Chetty, London N11.

QUESTION How many chemicals are there in human blood?

IT WAS once thought blood was made up of a few hundred chemicals, but it is now known to contain more than 4,000.

Blood is a fluid that moves through the vessels of a circulatory system. In humans it is made up of 55 per cent plasma (the liquid portion) and 45 per cent blood cells (99 per cent red blood cells, with white blood cells and platelets making up the remainder). Plasma consists mostly of water, with proteins, ions, nutrients and wastes.

Metabolomics pioneer David Wishart and his team at the University of Alberta in Canada have identified 4,651 chemicals in human blood. Metabolomics is a new science that identifies small molecule ‘metabolites’ — which are responsible for growth — in cells and organs as a tool in the early detection of diseases.

David Wellman, Colchester, Essex.

QUESTION Are there any comic sci-fi novels to rival the works of Douglas Adams’s The Hitchhiker’s Guide To The Galaxy?

FURTheR to earlier replies, I heartily recommend Philip K. Dick’s A Scanner Darkly, while Callahan’s Crosstime Saloon by the U.S.-born Spider Robinson is a must for anyone whose tastes run to bars, whisky, aliens and time travel.

And nothing has made me laugh like Diabolical Liberty, a gloriously funny fantasy romp by english author G. Llewellyn Barker.

Rob Cousins, London SE9.

QUESTION Was classical music played at a much faster tempo than it is today?

The earlier answer, which explained the technical reasons why music is played at varying tempos, reminded me of a story about Sir Thomas Beecham.

Following a performance of a Mozart symphony, the great conductor was asked why the final movement was played at such a high tempo.

he replied that the orchestra had been rehearsing all day before the evening’s performance and were getting tired.

Before starting the final movement, he had looked at his watch and realised the pubs would be closing in 40 minutes and his lads deserved a drink, so he whipped up the tempo so the orchestra would get to the bar in time. Bob Phillips, Bristol.