Hello Jean,
Excuse me for being a little bit pedantic but your initial message did not clarify what info you had so was posting the marriage date to avoid others having to search for it.    
 I take it you've contacted the other researcher in the USA who is also researching this family and has left their details on the IGI?
Children born to a Gilbert McAdam and Christian Duguid - Scotlandwide - from the IGI only between 1785 and 1825 are:
1.  ELSPET MCADAM Ch: 21 JAN 1793 Belhelvie, Aberdeen, Scotland 
2.  THOMAS MCADAM Ch: 06 OCT 1795 Inverurie, Aberdeen, Scotland 
3.  GILBERT MCADAM Birth: 20 FEB 1797  Ch: 04 MAR 1797 Inverurie, Aberdeen, Scotland 
4.  LOW MCADAM  Birth: 19 MAR 1803 Ch: 02 APR 1803 Inverurie, Aberdeen, Scotland 
5. WILLIAM MCADAM Birth: 28 OCT 1800,  Ch: 05 NOV 1800 Inverurie, Aberdeen, Scotland 
Cannot find Gilbert or Christian on the 1841 census at 
www.freecen.org.ukCannot find a Gilbert Mac/McAdam birth on 
www.scotlandspeople.gov.uk between 1740 to 1775
Regards,   Steve