Getiing delta between rows through SQL

[SANJAY_G]

Oracle 8.1.7.0

I have a requirement to ge the delta between rows. For example;

Column1   Delta
-------   ------
10        10
15        05
17        02
20        03
25        05
30        05
40        10

The column1 value is cumulative and it goes on increasing. I have to get delta between the rows. Is there any way I can do it using SQL.
TIA