A d.c. globule arc that hisses vigorously has been developed in conjunction with a direct-reading spectrometer built on a wavelength spectrometer and measuring intensity ratios by the null indication of a symmetrical cathode-follower bridge circuit. Self-electrodes are held in massive brass supports with the anode uppermost and the arc run until large molten globules form and stabilize on both electrodes. The relationship between the manganese concentration in carbon steels and the intensity ratio of manganese 4754 Å to iron 5455.6 Å is linear in the range 0.3% to 1.3% manganese, and standard deviations of 2% of content have been obtained. Standard deviations of 4% have been obtained by ordinary photographic photometry using manganese 4754 Å and iron 4707.281 Å. A method of preparing a working curve from a knowledge of the background intensity of the manganese line and a single standard sample is suggested. There is a discontinuity in the volt-ampere characteristic of the arc, but the curve is nearly parallel to the current axis at the operating point.