Scents and sensitivity

As he observes his cows on a warm August day, John Lewis-Stempel allows himself to be led by the nose and discovers that weather whiffing is no dark art, but proper science

- John Lewis-Stempel

I WAS leaning on the iron gate of the cow field, chewing a length of ryegrass, gazing at the occupants. The cows, bits of grass hanging from their slobbery mouths, regarded me. Mirror match.

Few animals exude contentment to the degree of an outdoor cow in summer and watching the Limousins engendered the usual contagious joy. But my hanging like a yokel on the gate was about more than self-help, a down-on-the-farm pick-me-up: survey a collection of cows for five minutes and you can tell which is sick and which is on the up (or down) in the herd order. Any cow off to the side or dragging behind is a cow in trouble.

All was well in the cow field. Particularly well… there was a euphoria above standard cow-watching. There was something in the air. It had rained 15 minutes earlier and the wet, bare ground around the gateway, where the cattle stand and stare, was releasing the odour of the earth. This particular scent, petrichor (‘Sweet with the evening rain’, August 3)—from the Greek petra, ‘rock’, and ichor, ‘blood of the gods’—is, to cut a chemical lesson short, a diffusion of aerosols containing the soil compounds, the most potent of which is geosmin. When it goes right up our noses, the 600,000 cells of the olfactory centre really rather like it. Primeval and musky, geosmin is a common ingredient in perfumes. Bottled delight.