The following plates come from a tiny book {4 inches by 4 inches] published in 1901 instructing both the 'sparkers' of the day and the greenies of the day {torpedo branch men} on matters of maintenance for Wireless Telegraphy Equipment.  The book covers Spark Transmitters, Crystal Receivers, batteries and accumulators, AC and DC switchboards and aerials.  I have chosen AERIALS because it covers just a few pages, and the PRACTICAL application would still be relevant today, whereas the same could not be said of the original transmitters, receivers and batteries.