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- 2~O :... I I I I I I I I I I I I I I I I I I I The zmc sulfide dispensing equipment is shown in Figure 13, To de- termine the concentration of zinc sulfide tracer in snowmelt samples, we developed the laboratory instrument shown in Figure l4. Samples from the various stations are collected in plastic boxe s and the contents decanted into sterile plastic te st tube s at the laboratory. Phosphore scence of the sample is determined by reading the oscilloscope amplitude in volts. Snowcrystal replicas were made during each storm to have a record of snowcrystal type s; the 1 % formvar in ethylene dichloride technique was used and the replicas air-dried. The concentration of silver in snowmelt samples was determined by the neutron activation technique under subcontract to Battelle- Northwe st Laboratories, Richland, Washington. Detection threshold with the present methods is of the order of 10 picograms. Freezing-nuclei count is monitored by a Bigg- Warner expansion cham- ber device at the Valley View Lodge, Figure 15. This equipment belongs to Colorado State University and is operated by a CSU observer, The readings are made at 0900 and 1800 each day as a control on CSU operations at Cli- max, Colorado. The CSU observer make s additional readings for us when conditions warrant. PRECIPITATION MEASUREMENT EQUIPMENT We use the optical snow-rate sensor shown in Figure 16 as our pri- mary measurement tooL A sample of its analog record is shown in Figure 17. The units are calibrated in the field by the spinning reticle shown in Figure 18, We use two heated tipping- bucket sensors on an experimental basis in the network and have one compressed- scale weighing gauge located at the laboratory. At each sensor location there is also a snowboard which is cor- ed and cleaned after each storm.