An interesting item from Horsecars: City Transit Before the Age of Electricity, by John H. White, Jr.:
In 1881, New York City streets received 2.5 million tons of manure and 60,000 gallons of urine.
Any thoughts on this?
UPDATE: Bing bing bing! Johan Bakker (in an e-mail) and Rick Felt (in a comment) got it at pretty much the same time, though Felt's was the sixth comment. (Got the rest of you. Bwa ha ha ha.) This quote can't possibly be right, as a quick bit of arithmetic reveals: 2.5 million tons is roughly 5 billion pounds, and 60,000 gallons is roughly 0.5 million pounds. Can a horse's manure exceed its urine by a factor of 10,000? Surely not.
So when I first noticed this problem -- as I was copying and pasting the quotation into a draft article of mine -- I asked the UCLA Law Library to track down some other data for me. And sure enough, here's what I get from James J. Flink, The Car Culture 34 (MIT Press, 1975) (though unfortunately without a specific citation): "In New York City alone at the turn of the century, horses deposited an estimated 2.5 million pounds of manure and 60,000 gallons of urine on the streets every day."
Now that seems much more plausible, with manure exceeding urine by a factor of 5 rather than 10,000. I'm not a horse expert, or a historian of New York horse transportation, so I can't be sure that this is right. But it certainly seems less likely to be wrong than the line that I initially quoted.