Now that it seems likely a comet has drawn a sharp line of charcoal between the two cultures, careful measurements should be able to show whether North America was, for a few centuries after the impact, as bereft of people as it has since been of mammoths.
Opposition spokesman Lord Bach said any amendment proposed by the two peers deserved "careful" and "sympathetic" consideration because of their experience and backgrounds.
He will arrive in London with even more experience under his belt and, with two more years of careful preparation, he believes that the ultimate prize is now within his reach.
The document will remind careful readers about two facts of Internet life.
But the two men had been extremely careful about covering their tracks.
You have to be very careful because there are two things that could be happening.
The government is being careful because more than two-thirds of Buy Korea investors are first time mutual-fund buyers.
Not only do you have this two year warranty, people are very careful indeed to tell you that you do have it.
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As president, he announced a careful six-year programme: two years for the economy to recover, two years for stabilisation, two years to leap forward into greatness.
Although there is nothing inherently funny about two people being romantically thwarted for nearly two decades, Waiting turns, page by careful page, into a deliciously comic novel.
President Obama, who has been in office for five months, has been treading a careful line on Iran, which has seen two weeks of street demonstrations following a disputed presidential election there.
But these two plus points could quickly become minuses if they are not careful.
All I can tell you is it was made after very careful consideration based on the need to balance those two issues and that the necessity to provide access to preventive services for women was an important consideration.
In his two years in office, Chief Executive Tung has been necessarily careful to demonstrate to the central government in Beijing that Hong Kong is sufficiently "patriotic" to be left alone to get on with its own business.
There are also two contestants from war-torn Syria, though both have been careful not to take sides.
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Be Careful before entering the pair trade to make sure the two assets are diverging from each other.
"We came to our decisions to issue the Hinkley Point C permits only after careful consideration of all the responses we received following the two periods of public consultation, " a spokesperson for the agency said.
Liverpool managing director Ian Ayre said the club gave "careful consideration" to ticket prices and pricing over the past two years.
There are two schools of thought and the one people need to be a bit careful of is that if you try to make him something that he's not, you make him less effective as a player.
Two rain breaks in the second set disrupted Ivanisevic's rhythm but some careful baseline rallying in the tie-break forced errors from Youzhny.
It's my cue to be careful -- to steer clear of red wine and sugar, two sure triggers when I'm in that sensitive state, and to get enough rest since lack of sleep can tip me over the edge, too.
With the two coxes both vying for the same quick water, they have to tread a careful path between giving their crews the fastest conditions, and also the clearest run - which can sometimes have calamitous results.
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If JAMA is not careful how it implements its new policy, that may yet work against the first two goals.
If there were three cell phone providers and two of them wanted to merge, that would still be something for antitrust authorities to give careful scrutiny.
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"I think this time last year, or two years ago, we would certainly have got a mortgage, but now they are being very careful, " Andy says.
So far, the Bush administration has threatened North Korea, not with war, but with further isolation including, with help from other countries, the interdiction of shipments of the missiles and illegal drugs that finance its nuclear habit and growing pressure to suspend construction of two civilian nuclear reactors that were part of the 1994 deal although George Bush has been careful not to rule out force.
''Careful management of the small population here in Newquay has meant that the time has come to return two animals to their native home.
"I'm more careful about my diet now, I exercise regularly and I've not had any alcohol for about two and-a-half years, " he added.
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