You should be fine BUT as jivdis1x indicated YOU observer the Correct polarity.
Most Laptop AC adaptors are 19 volt and can provide upto 4+ amps.
The regulator circuit is inside the laptop. The AC adaptors may have around 22 V out with no load and as the load current increases the output voltage drops.
Most laptops come with a car addaptor which only approx 13.6V, but current may be higher than the 4+ for an AC adaptor.
Thank you Chief for the info. Prior to posting, I checked the voltage 19.4V and the adapter is rated for 90 watts (the Gateway takes only 65 watts). I will pay attention to the polarity and ensure that the spliced wires (splices) are staggered.