ELECTRICITY in a vacuum, sparks, arcs and microscopes is the title of this year's Tyndall lecture which will be given by Dr Bryson Gore today at 2.30 p.m. in the RDS. While members of the public are welcome, the lecture is particularly aimed at second- and third-level students. Admission is £1. Further details from Bridgeen McCloskey, science development executive, RDS (tel: (01) 668 0866.