Subject: vapor pressure and boiling point

I have read a lot of material about vapor pressure and boiling point, but 
I still can't understand something about an experiment my class conducted 
in school.  We boiled water in a stopped flask that had a tube coming out 
of the side which carried the steam/vapor out.  When the water boiled we 
measured the temperature (@99ºC) and then placed the "vapor" tube in cold 
water.  The temperature in the flask increased to 100ºC.  I know that in 
order for that to happen the internal (in the flask) vapor pressure must 
have been raised or the external pressure must have been raised...but 
how?  How would sticking the "vapor" tube in cold water change any 
pressures?  I really hope you can help me, and this is a wonderful service 
you have!  Thank you!!

Re: vapor pressure and boiling point